How many Yamaha RD350 crankshafts has Kevin Cameron rebuilt? How many cylinders ported? KC and Editor-in-Chief Mark Hoyer talk about Yamaha’s sporty and quick two-stroke twin, from its origins in the 1960s all the way to the RZ350 of 1985. Hoyer’s first streetbike was a 1979 RD400 Daytona Special—lots to cover. Breathe deep!
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SportsTranscript
00:00:00Ignition.
00:00:01Ignition.
00:00:02Welcome back to the SAG World Podcast.
00:00:05I'm Mark Hoyer, Editor-in-Chief.
00:00:06I'm with Kevin Cameron, our Technical Editor.
00:00:08This week's topic is one near and dear to our hearts, the Yamaha RD350, RD400, probably
00:00:17the RZ350 and maybe it's barbell crank.
00:00:21Yes.
00:00:22But really starting with the Yamaha two-stroke twin, which is the stuff of legend, RD350
00:00:31is known as the giant killers.
00:00:32They were lightweight.
00:00:33They had chassis geometry not far off of the TZ350 race bikes.
00:00:40They formed the basis for TZ750s and et cetera, and they were easy to work on.
00:00:48They were lightweight.
00:00:50To be made to make a lot of power, I dug into the archives and found Yamaha racing
00:00:58tips, loose leaf binder, three ring, also Yamaha racing parts for you spotifiers.
00:01:08I'm holding up beautiful yellow and black bumblebee binders with, I don't know, two-stroke
00:01:16Bible stuff in there.
00:01:19Special tools and how to use them.
00:01:22So yeah, that's beautiful.
00:01:23In this wonderful 1960s style.
00:01:27Yeah.
00:01:28So Kevin's got obviously a lot of experience with all this stuff and he has even more paperwork
00:01:34than I do.
00:01:37What happened in the beginning was that everybody's got to do a twin eventually because singles
00:01:43just you make them bigger, you run into trouble.
00:01:47Yamaha had as an inspiration, a German Adler twin, and they did not copy it.
00:01:58They didn't like the fact that it had only four speeds, so they had five speeds.
00:02:02They didn't like the method of attaching the two crankshafts together with a hearth coupling
00:02:07and a big draw bolt.
00:02:10So they went to a press fitted inner pair of crankshaft flywheels.
00:02:15A lot of things were different on Yamaha's early twins, but the one that hit the market
00:02:21and really caught a lot of attention was the YDS-2.
00:02:29And the YDS-2 was built like the Adler on a vertically split crankcase, which meant
00:02:35if you imagine the crankshaft floating in midair with all its bearings and spacers and
00:02:40the two cases are coming closer and closer with Yamaha special tools to draw them together
00:02:47and you, oh, I forgot to put the gasket sealer on, let's take it apart again.
00:02:52And eventually those vertically split engines went as far as the TD-2, which had four transfer
00:03:01ports and it was really fast.
00:03:05In 1969, Yamaha decided to experiment with a horizontally split engine, and this was
00:03:11the R1-350 of 1969.
00:03:16And it was built like rational engines.
00:03:19You had the lower case, you set the crankshaft and all of its business in there.
00:03:24Just a really easy to organize tray to put your parts in.
00:03:26It's really awesome.
00:03:27Excellent.
00:03:28Excellent.
00:03:29And then the gearbox shafts and the kickstart shaft.
00:03:33You didn't put the top case on, or if you built it the other, you built the other way.
00:03:39But once it was together, all you had to do is put on the clutch, the ignition and outer
00:03:43covers and you were done.
00:03:45Cylinders, you'll want those.
00:03:48But those three years of 350 twins, mind you, all these engines are air cooled, were a learning
00:04:00experience for Yamaha.
00:04:02And then in 71, I think, they produced the R5, which was an evolved 350 twin.
00:04:14And they had a bright idea.
00:04:16They said, we could build modular engines.
00:04:20They will all have the same 54 millimeter stroke.
00:04:23The 350 twin will have a 64 millimeter bore and the 250 twin, a 54 millimeter bore.
00:04:32And thus it was.
00:04:35And in fact, when TZ750 was built, 750A was built for the 1974 season, it had the 54 millimeter
00:04:44stroke and the 64 millimeter bore of the R5.
00:04:49Now the R5 was a piston port engine, meaning that the rising and falling of the piston
00:04:55opened and closed a hole through the cylinder wall, the back of the cylinder.
00:05:01There was a carburetor there so that when the piston rose, the pressure in the crankcase
00:05:05below dropped.
00:05:07And when it opened the port, there was a pop, a pulse of air went through the carburetor,
00:05:13picked up fuel into the crankcase.
00:05:16And then when the piston came down again, it compressed that mixture in the case until
00:05:25the piston uncovered transfer ports in the cylinder, the air in the crankcase came up
00:05:30through those transfer ducts to fill the cylinder.
00:05:34Yeah.
00:05:35So we're talking two strokes, maybe most of you listeners based on what we see in comments
00:05:40probably have a pretty good idea about it.
00:05:43But, you know, pre-mixing oil and gas, you know, a lot of these had 350s and you had
00:05:49oil injection, you poured your oil in a tank and there was a little pump that was dripping
00:05:53oil in to lubricate all the bearings.
00:05:55But strictly speaking, you were pre-mixing a lot of times with two strokes to lubricate
00:05:59all the bearings in the engine.
00:06:00So that's going into the crankcase with that suction and a transfer port is a hole, is
00:06:05a port that goes from the cases around the cylinder up to where the chamber is and gets
00:06:12shot in there so you can light it on fire and...
00:06:15Imagine a mug with two handles.
00:06:17Yeah.
00:06:18And the handles are hollow.
00:06:19The handles are the transfer ducts.
00:06:20Yeah.
00:06:21But, and the R5 was a five transfer, yes?
00:06:27I can't summon that piece of information.
00:06:29I believe it was a five transfer in the...
00:06:32It would make sense that it would be because it was the new era.
00:06:35And then the 350 was seven, correct?
00:06:39It was a tremendous piece of work and a lot of people liked them.
00:06:45They were produced for, what, three years?
00:06:48I think they made 25,000 of them or so.
00:06:53And then Yamaha was consulting with all these reed valve people.
00:07:01I think they had some conversation with the late Dale Herb Branson.
00:07:07And they put reeds on, reed intake, which is like a one-way valve based up like a saxophone
00:07:13reed backwards.
00:07:16So that made the engine easier to manage at lower RPM where the exhaust pipe wasn't doing
00:07:26much pumping.
00:07:28And the thing about the RD350 was that, mind you, this is the early toward the mid seventies.
00:07:38English business practices had put a lot of nails in the coffin of British motorcycling,
00:07:45but motorcycles like the RD350 added a whole bunch more because being lighter than what
00:07:53used to be the hottest of the hot and having pretty good horsepower.
00:07:58I think I see a claim for 39.
00:08:01I think these RDs would give a good challenge to a lot of British twins and certainly to
00:08:10when well-ridden to a big inch sportster.
00:08:15So some people have called the RD350 the first sport bike.
00:08:21That's nonsense because the Kawasaki Z1 was arriving at that time, but it was something
00:08:31that was a lot more affordable than those new monstrosities and it brought high performance
00:08:38to a great many riders.
00:08:40Easier to modify too.
00:08:41I mean, you're starting with a big four cylinder, you know, I mean cylinder head porting and
00:08:46valves and I mean, needless complication.
00:08:53So what you did with an RD was to get each head off, you undid four sleeve nuts, pull
00:09:01the head off the gasket, slide the cylinder up and take the carburetors off first because
00:09:06they're in the way and the exhaust pipes, and you've got cylinders in your hand and
00:09:11then you can raise the exhaust ports.
00:09:14You can widen them.
00:09:15You've got the cylinder heads, look at that, and this circle, this circle here, that's
00:09:26the squish band.
00:09:27Yeah, he's pointing to the squish band.
00:09:29So he's got an RD350 head, I'm assuming RD350, but it's the two pieces, the 350s had a cylinder
00:09:36head for each cylinder.
00:09:37The RD400 had a single piece kind of more like a shaped like a scoop.
00:09:44It was emission controlled, the 400, this one had an exhaust valve that made the head
00:09:49a little hotter.
00:09:50So they were trying to improve cooling and give it more surface area and all that.
00:09:52But this is a single cylinder head and he's showing the combustion chamber, which is round.
00:09:57You could chuck that up in a lathe, I bet.
00:09:59A lot of friendly machine shops had a mandrel with a 14 millimeter, one and a quarter millimeter
00:10:06thread.
00:10:07You just put that mandrel in the lathe, spin this thing on there, and then you're ready
00:10:11to take 25 thousandths off of this gasket surface and your compression up, up.
00:10:17Up, up, up, and then bang, you're getting a little more pop out of here.
00:10:21But that's how you know you're sincere.
00:10:23You've got to buy pistons in order to learn that business.
00:10:27That's the way it was.
00:10:28That's why the phrase fresh pistons, I imagine all these people looking like poor downtrodden
00:10:36seasonal workers moving slowly through the piston fields in the misty morning, getting
00:10:42fresh pistons.
00:10:43Fresh pistons, plucking them from the trees.
00:10:46Yes.
00:10:47But when the thing is that if you had a clue what you were doing and you had some basic
00:10:54tools, not a cam grinder, you didn't have to be an industry, you could boost the performance
00:11:04of an RD350 or a 400 way up.
00:11:09Let's buy pipes.
00:11:11Let's put 34 millimeter carburetors on.
00:11:13A lot of people did, and I did it for them too.
00:11:20But it was a transformation because from whatever the horsepower was, it went up about 25 percent
00:11:27and you had something.
00:11:29And it was unfair.
00:11:31In racing, the guy that was finishing third would come to me and he'd say, can you help
00:11:36me out?
00:11:37So I'd go with the die grinder and he'd phone me up and say, oh, it's great.
00:11:44I won the last race and the other guys have to come and have theirs done and in the end,
00:11:49the good rider wins.
00:11:52So all that was happening was that I was this parasitic creature sapping their funding.
00:12:00No, you raised their performance level.
00:12:04You're the bearded wizard in the shop, showing them the path to freedom.
00:12:09Used to be the cellar dweller.
00:12:11Well, it was a lot of fun.
00:12:14And people spent many happy hours squatting or sitting cross-legged on the ground next
00:12:24to their bike on the stand, setting the ignition timing.
00:12:30And the way you did that was Yamaha special tool dial gauge adapter.
00:12:38This screws into the spark plug hole.
00:12:41Dial gauge goes in and is fixed with a set screw.
00:12:47On the dial gauge is a pointer.
00:12:49As the piston comes up, I've not put in the little probe here, as the piston comes up,
00:12:54you see the dial gauge swing around, stop and then go back.
00:12:58As the piston reaches top dead center and passes it.
00:13:02So if you want ignition at two millimeters before top center or 2.05, you back the piston
00:13:09down to where the pointer says that number and you could be sure that you were doing
00:13:16it right.
00:13:18And it was nice to think of dinner at the same time.
00:13:23Put these bikes away.
00:13:24They're ready for tomorrow's morning practice.
00:13:27We're going to have a ball.
00:13:28Well, I mean, the modification you said, well, you know, if you had an idea of what you were
00:13:35doing, you didn't even need to have an idea of what you were doing.
00:13:38You could wreck these things and rebuild them real easy.
00:13:40I mean, you could melt the piston, you know, what you were saying again in under an hour.
00:13:45Yeah.
00:13:46Four bolts, take off the head.
00:13:48Four bolts per carburetor, take off the carburetors.
00:13:51If you had expansion chambers, usually there's a spigot bolted to the cylinder and then it's
00:13:56just springs and you undo the springs and slide your pipes out of the way.
00:14:00And you were in the engine.
00:14:01No cam chains, no flimsy little push rods to get flung out.
00:14:07No cam shafts, no cam grinders.
00:14:08You just did your thing.
00:14:10And in mere minutes you were inside.
00:14:12So they were really easy to work on.
00:14:15You could melt the piston.
00:14:16You could buy a piston.
00:14:17Gosh, they must've been nothing or they would seem like nothing now, but it is really nice.
00:14:24Little rings, not really too worried about oil control.
00:14:29Little hydrochloric acid on the cylinder wall to get the aluminum off and you're going.
00:14:36In the early days, so many people went production racing with RDs and some stiff necked racing
00:14:44organizations insisted on stock foot pegs.
00:14:48And the original foot peg brackets came out from under the mufflers so that if you lean
00:14:55the motorcycle over like you're a racer, it would lift your tires up and you would slide
00:15:00off the racetrack.
00:15:02So people adopted an exaggerated Mark Marquez body to the inside style.
00:15:13People used to joke that RD riders, you could see the hiking straps hanging out of the back
00:15:19pockets, like were used on one design sailboats.
00:15:26And finally the message got through and non-stock foot pegs were permitted.
00:15:33Well, I heard stories of guys just bashing them with hammers, just putting different
00:15:38pipes on so that they would clear and then bashing the foot pegs with hammers to just
00:15:43They were, yeah, they were stock.
00:15:46They were just...
00:15:48Or a body grinder with a coarse wheel.
00:15:53So they were highly active classes, stock class, modified class, of course.
00:16:00And that was what a lot of people did in club racing, RDs, in the days before the second
00:16:10generation of four-stroke sport bikes, or really before the sport bike, the smaller
00:16:17sport bike, gelled in the form of the Honda Hurricane and the various Ninjas and Seikas.
00:16:25So it was a valuable vehicle for people who wanted to race something that was close to
00:16:36a racing performance and yet was really inexpensive to operate.
00:16:42And there's one of those rules of thumb for the amateur racer, don't race anything you
00:16:49can't afford to crash.
00:16:52And this is the hard thing for people who go to track days because they, of course,
00:16:58they want to look good.
00:16:59They've paid a lot of money for this beautiful motorcycle and they want to look good.
00:17:03But if they're not going fast, they don't look good.
00:17:08And if they crash, oh, oh, just look in the Ducati accessory catalog.
00:17:15It is so wonderful.
00:17:17Is there a reason to want to be rich?
00:17:19Yes, that catalog.
00:17:23All that gleaming carbon fiber stuff and the titanium parts and the...
00:17:29Well, that's nothing to do with RDs.
00:17:32The thing about RDs is every person's race bike.
00:17:37And there were plenty of women riding them too.
00:17:41Maybe not plenty, but there were enough that it was no longer remarkable.
00:17:45So...
00:17:48Yeah, stock RD350 is a beautiful size, compact human size, easy to handle.
00:17:55344 pounds is what we weighed our test bike in 1973 with a half a tank of fuel.
00:18:02344, not bad.
00:18:03No, that's not bad.
00:18:05And the stock setup on those stock pipes, stock carburetors,
00:18:10they're Makuni 28 millimeters on the RD350 round slide.
00:18:16And they were pretty torquey.
00:18:17I mean, they were really...
00:18:18It was kind of a nice street bike.
00:18:19They made good power pretty quick.
00:18:21I think our slides like these.
00:18:23Yeah, exactly like that.
00:18:27Standing quarter mile was 1430 at 89.82.
00:18:31That's pretty darn quick.
00:18:33Yeah, it is.
00:18:34400, the 79 RD400 wasn't much quicker than that.
00:18:38Just barely 1418 at 91.37.
00:18:43So, you know, good performing.
00:18:45But also you could completely change the power with pipes and porting.
00:18:50And you could go up in carburetors, carburetor size.
00:18:57The way people use them had a lot to do with changes in the motorcycle.
00:19:01Over the three years when they started out, the crank pins had holes through them.
00:19:08And of course, the reason for a hole is you don't want
00:19:11to have to put any more counterweight than you have to on the crankshaft.
00:19:15But all these dark marks on here are the result of slippage.
00:19:23Slipping in the press.
00:19:26In the press fit.
00:19:28And what some people...
00:19:30I remember this started to happen in a big way with the RD400 in modified racing form.
00:19:38A fellow called me up and he said, a weird thing is happening to my bike.
00:19:42He said, I always check the connecting rod side clearance after every weekend,
00:19:47which is, as we previously observed, easy to do.
00:19:50You just take a feeler gauge, put it down between the connecting rod and the crank cheek.
00:19:56And he said, my side clearance on the ignition side is increasing every weekend.
00:20:03And he said, what happens when it gets really big?
00:20:06And I said, you'll lose the main bearing on that side and your engine will seize.
00:20:11Yeah, I don't want that.
00:20:14So Yamaha's response was a solid crank pin, which increased the strength of the press fit.
00:20:23Maybe we could talk about that just for a moment because
00:20:27I think we're all so informed of looking at the insides of four strokes,
00:20:32modern four strokes with plain bearings and split connecting rods.
00:20:36And you have fracture split rods that fit perfectly and all of that nonsense.
00:20:41But this was a pressed together crankshaft.
00:20:43So you had a cheek with a shaft on it that was your ignition shaft or whatever.
00:20:49And then you put a bar in it and you put your connecting rod,
00:20:55which was a complete circle with a bearing, and you slid that on the shaft.
00:21:00And then you set up your business in a big press and you pulled your lever,
00:21:04hydraulic press, and then you started to jam that sucker together.
00:21:08And if you're smart, you have some, you know,
00:21:11jig type stuff to align up your crank wheels so that they're not so far out.
00:21:15You don't want them to be.
00:21:17Yeah, you don't want to be out of alignment.
00:21:19So you kind of get them lined up and then you'd put the,
00:21:23you build up your stuff and you press it all together.
00:21:25And that was it. It was just pressed together.
00:21:28The XS650s were like that as well.
00:21:30And all the race guys would weld them, you know, so they didn't, I guess, fly apart.
00:21:35But they hoped, they hoped.
00:21:37They hoped, yes.
00:21:38And so you would press that whole crank together.
00:21:41And then you'd have a rebuilt crankshaft with the new bearings and new connecting rods.
00:21:45And you'd slap your pistons on and you'd drop that in your engine case and away you went.
00:21:51I was at a race in Thompson, Connecticut.
00:21:54And a guy I knew slightly at the time went by rolling his bike,
00:21:59which seemed to be pretty warm.
00:22:01I seized it, he said, but I have a crank.
00:22:05And 45 minutes later, he came by, engine running.
00:22:11He'd changed the crankshaft.
00:22:13Making popcorn.
00:22:15That's why they were so attractive.
00:22:18Because there were a lot of people that knew how to, knew their way around a simple engine.
00:22:25And they weren't afraid to just dive in there and do stuff.
00:22:30And so changing a crankshaft in 45 minutes was possible in those engines because they were simple.
00:22:37And you could, if you knew the dealer decently well,
00:22:40you could have a crankshaft sitting in your box for a hundred bucks.
00:22:46Not bad.
00:22:47Not bad at all.
00:22:481973.
00:22:50So that method of constructing a crankshaft is still in use today, but in only very limited use.
00:23:01I think Honda's 450 has a pressed together.
00:23:04The motocross engine has a pressed together crank.
00:23:07And the handbook that I remember looking at said that Conrad Big N Life was 10 hours.
00:23:15And that's about right.
00:23:18If you're going to insist, if you're going to push things to 10 or 11,000,
00:23:23the bearings are eventually going to just get real tired of that action.
00:23:28And you'll rattle to a stop having pulled the clutch.
00:23:35And, but it was, there were a lot of people having a good time.
00:23:40They had a good idea of what they were doing.
00:23:44And it was a community.
00:23:45If you needed a piston, somebody, two vans, three vans down on one side or the other had a piston.
00:23:51Oh, it's first oversize.
00:23:52Yeah, I've got that one too.
00:23:55So good fun in that time.
00:23:58Well, you know, years ago, I sent my RD350 engine to you in the mail.
00:24:04And, uh, flew out and we rebuilt it in your shop.
00:24:08And, um, it was cool because we found actual problems.
00:24:11You know, this, this was an RD350 I bought off of eBay.
00:24:16First story, a thousand dollar bikes on a thousand mile ride.
00:24:20And, um, the eBay listing was a big lie for salad dressing in the carburetors.
00:24:27My cam, uh, my, uh, my points cam had been sitting in one place with a wet felt for so
00:24:34long.
00:24:34It was deeply pitted.
00:24:36So I had to get, I had to get a new, uh, a new, that was, that's the cam that opens the
00:24:41points.
00:24:41It's on the end there.
00:24:42And it kicks your points.
00:24:45So far out from the bearing that it magnifies its error.
00:24:50Yeah.
00:24:51And so I sent that out to you.
00:24:52And so we found real problems.
00:24:54It was a bike that had been ridden quite a bit and it had pitting on the six gear.
00:24:59Um, teeth, you know, and it had been running six quite a bit.
00:25:03I had to order gears.
00:25:04I order, I had to call a guy who had a gear set and he sent them out to us while we were
00:25:09doing all of that.
00:25:11I think it was one of my most humorous, uh, failures to communicate between you and I
00:25:18was, you know, I wanted to modify the bike.
00:25:21That's why I sent it to Kevin's shop.
00:25:23And I flew out to work on it with him as I wanted to modify my RD three 50 with Kevin
00:25:28Cameron's wizard, like porting.
00:25:30So I could win the race.
00:25:32And, um, as long as I was the rider to do it.
00:25:35And, uh, we talked about what, what to do, what to get.
00:25:41And I said, well, you know, it's 28, 28 millimeter carburetors.
00:25:44I'm going to get some flat slides, some Acuna flat slides.
00:25:47You know, I was thinking thirties, maybe thirty twos.
00:25:50And Kevin said to me, well, I guess if you want to put those wee little things on your
00:25:54engine, you can.
00:25:56And so when Kevin Cameron says, put thirty fours on it, you get thirty four.
00:26:00So I got thirty fours and, um, came out and I was just over on the other side of the shop
00:26:07cleaning the cases.
00:26:08And you had the cylinders, you had your little glasses on and you had your porting tool and
00:26:13you're over there with your octopus hanging from the shop ceiling or whatever, the rod,
00:26:18all the different cutters and doing all of that.
00:26:21And you're talking about how you cut into the port, not into the cylinder, because if
00:26:26there's plating, you don't want to lift the plating.
00:26:28You want the cutter to lay the plating, keep the plating flat, et cetera.
00:26:32Lots of little tricks.
00:26:33Got towards the aluminum.
00:26:35Yeah.
00:26:35Yep.
00:26:35And so he's over there doing that and I'm cleaning, chasing threads and then, um, he's
00:26:41just hogging away.
00:26:44And he finishes and I say, well, Kevin, that's cool.
00:26:47How'd it go over there?
00:26:48Yeah, really good.
00:26:48We had some big action.
00:26:50We, we, uh, got out into space.
00:26:51I had to put a bolt in, uh, in the transfer, put a, you know, he puts a bolt in, pack some,
00:26:56uh, you know, quick steel around it.
00:26:58Epoxy keeps cutting.
00:27:00We've patched the hole and I said, uh, yeah.
00:27:04So what's the power, you know, cause when I talked to Kevin, I said, I want a torque
00:27:07motor, you know, I'm just going to ride this on the street.
00:27:08I want a pretty good, pretty good torque.
00:27:10And he's like, oh, well my, my motor's always made a little bit more torque than Irv's.
00:27:14And Irv, Irv had, Irv, Irv aimed his ports, you know, at each other, I think.
00:27:19No, they were, they were up.
00:27:20Up.
00:27:21Okay.
00:27:21So they were up and then Evan and then Kevin pointed his at each other.
00:27:25A lot of flow on top.
00:27:27So the engines were really strong.
00:27:29Yeah.
00:27:30And so.
00:27:31But only Freddie could drive them.
00:27:32Yeah.
00:27:33So I say in the beginning before porting, yeah, I'm looking, you know, torque, you know,
00:27:39I want a torque motor.
00:27:39Kevin says, yes, I built, I built a torquey motor.
00:27:43And so he finishes all of that and I say, yeah.
00:27:45So what's the power going to be like, you know, like three to seven, six to nine and
00:27:51you know, five, five, what is it?
00:27:53Three.
00:27:53And I was thinking like, yeah, it's going to make power at 4,500 to 7,500 or something
00:27:58like that.
00:27:59And he says, he looks at me, it says four for the big question, four.
00:28:06And he's like, no, six to 11.
00:28:08And you're going to have to get rid of the stock ignition because it'll slowly walk off
00:28:11the crank apart.
00:28:14Yeah.
00:28:14It was like, just like that was our failure to communicate.
00:28:16So I was getting a full race, you know, whatever it was, TZ, TZ spec, you know, full race,
00:28:21let's cut wood, power comes on, let's go.
00:28:25And that's what we got.
00:28:25So that's what we have.
00:28:27Well, the thing is the stock RD peak power is at 7,500 and peak torque was at seven.
00:28:35So it wasn't what you'd call a broad torque engine, even in stock form, but the reeds
00:28:42helped, I guess, if you were having to obey the laws in an urban area, it made it into
00:28:51a docile scooter.
00:28:53But if you've got a good ignition and you have your carburetion close, you can make
00:29:01it run.
00:29:02So it was, it was an amusing thing though, because normally those RDs, people did rev
00:29:15them to 10, 10, 5, 11, and the heavy stock ignition rotor slowed down the elephant ears
00:29:24flapping mode of the two flywheels on the ignition end of the crankshaft.
00:29:28So that the flywheel slowly slid off of the crank pin, like four thousandths, six thousandths
00:29:39per weekend.
00:29:41And the fix was easy.
00:29:44You put on a racing type ignition with a very light rotor.
00:29:47It raised the frequency beyond the firing frequency so that there was no longer, they
00:29:53weren't humming, they weren't on the same page of music.
00:29:57And no more walking off the crank pin.
00:30:01So fun times.
00:30:04The stock engines for a long time came with connecting rods that did not have slots in
00:30:09them for fuel air mixture, notably fuel, to be thrown directly onto the rollers.
00:30:18You could look through the slot and see the rollers.
00:30:21So for a time there was a business of using a big abrasive disc to cut slots in the rods,
00:30:30but it was easier to just get the TZ rods in the first place because it was the same
00:30:35forging.
00:30:38You should have seen your face when I handed you the bearings that I had bought for my
00:30:42connecting rods.
00:30:43Oh, did I make a face?
00:30:45And you said, oh, how about we use these?
00:30:48And he disappears into the back of the shop, walks around the 4360 radial aircraft engine,
00:30:55and comes back with a TZ silver plated.
00:30:58So these are better.
00:30:59We'll use these.
00:31:02Well, people did crazy things with 350s and 400s.
00:31:06I worked with a guy who had his motor souped up.
00:31:10He had an aluminum swing arm.
00:31:11He had a TZ style gas tank.
00:31:14He had everything that he could spend money on.
00:31:16He spent it.
00:31:18I said, well, you know, you could put TZ style foot valves in the bottom of your front fork
00:31:24diff.
00:31:25Oh, yeah, I got to have those.
00:31:27On and on.
00:31:28Well, it was a sport for him, and he enjoyed every minute of it.
00:31:32He wasn't a particularly fast rider.
00:31:35There was a day at Bridgehampton on Long Island when he had this modified monster, and he
00:31:45said, I think there's something wrong with my bike.
00:31:49I'm lapping around 2 minutes 10, 2 minutes 12.
00:31:55And I said, why don't we get Dave Roper to ride it?
00:31:58He loves to ride anything, and he'll give you an unvarnished opinion.
00:32:03Oh, yeah, that's a good idea.
00:32:07So Roper goes out on the thing, and he comes humming past a couple of times.
00:32:14Third lap, he comes in, and he's done a 2.03, I think.
00:32:20And Roper gets off, hands him the bike, and says, nice little bike.
00:32:27And the guy was crushed.
00:32:30Yeah, wouldn't it be crushing?
00:32:32But these social circumstances must be avoided.
00:32:36He's a talented rider.
00:32:37Still is.
00:32:38The terrible thing about all of this is racing is a hard collision between human beings and
00:32:47the physical world, because if you're not fast, it'll show.
00:32:53And that's the great thing about racing is that the people who are up front have learned
00:33:02how to do it.
00:33:04They learned.
00:33:05They aren't taking risks.
00:33:06They aren't daring speedmen.
00:33:09They learned how to do it.
00:33:11And that's the wonderful thing about the RDs.
00:33:14And all of that low-budget racing is you're learning to manage life on two wheels.
00:33:22And it's the same as it is in Grand Prix racing.
00:33:26It's the same predicament.
00:33:28So you're in the zone if you're going well on your cranky old modified two-stroke.
00:33:40Or indeed, if you're on a CB350, Honda four-stroke, same era.
00:33:49They sold the daylights out of those things.
00:33:51So many.
00:33:53And of course, the vintage racers have bought up all the ones that still remain.
00:34:00Same thing with the RDs.
00:34:01It's just been a...
00:34:03There was a madness.
00:34:05Then there was 2008.
00:34:07Then there was COVID.
00:34:09And we don't know what's next.
00:34:15So the 350 then turned into the 400.
00:34:19And that was just...
00:34:21They were dealing with the kind of nascent emissions business.
00:34:29They put a valve in the exhaust ports.
00:34:33I don't remember that on the 400, but I sure do on LC.
00:34:37Yeah, it was on the RD400.
00:34:40That was my first motorcycle.
00:34:41It was a 1979 RD400 Daytona Special.
00:34:45I never saw that.
00:34:46My neighbor owned it.
00:34:47And it was 100% stock, had 9,000 miles on it.
00:34:51And I bought it from him and started riding it around.
00:34:55I did high side it.
00:34:57It was my first bike and my first high side, as many RDs were totaled.
00:35:02This one I bought.
00:35:04It was stock.
00:35:05I took it to some pipe guy up in Pomona to build chambers for it.
00:35:11His name was Tommy Crawford, a Grand Prix tuner
00:35:17who was doing a pipe business, retired from racing.
00:35:20I think he worked on Suzuki's quite a bit.
00:35:23TC Exhaust and built these beautiful chambers for it.
00:35:26Repackable mufflers with a big circlip to take the packing out of the back.
00:35:31They sounded great.
00:35:32And man, did that thing.
00:35:33It was a good street pipe, ran strong, ran great.
00:35:36And then I crashed it and wadded it all up into bits.
00:35:40And that's when my parents said motorcycles were water under the bridge.
00:35:44And I say, ha ha.
00:35:47And where are you today?
00:35:49Yeah.
00:35:51But it was great.
00:35:52It was at the time when I bought the RD.
00:35:55Oh, that was the point of the story is I went to pick it up from Tommy.
00:35:58And I was a kid, I was 16 years old.
00:36:02And he said, your wheels, we just, your rear wheel was out of alignment.
00:36:07I'd never taken the rear wheel apart.
00:36:08I was still on these chintzy old worn out tires that the bike came with.
00:36:13And he's like, we straight, you know, the wheel, it was a little crooked.
00:36:15So we straightened it out for you.
00:36:16And, you know, you lined your wheel up.
00:36:17Did it feel like it was crabbing?
00:36:19I'm like, I don't know.
00:36:20You know, I was, I can barely ride the bike.
00:36:23So I had no idea that, that the wheel was out of alignment, but he did that.
00:36:26And then he said, and by the way, you have this exhaust valve and it was wired open.
00:36:31And then they just cut the threaded rod that was controlling the, the butterflies on it.
00:36:37They just cut it, wired it open.
00:36:39And that was that.
00:36:40And, uh, and then I had my chambers ran great.
00:36:42It was really fun at that point.
00:36:44Um, and then of course the, we had a wall in the United States until, uh, RZ three 50,
00:36:5384, 85.
00:36:55And, uh, that's when we got the liquid cooled three 50, lots of power had catalytic converters,
00:37:02lots of heat, lots of heat, much, much heat.
00:37:06And, um, the fuel and the cylinders and the rest of it in the pipes.
00:37:13Yeah.
00:37:13And making some, making some real heat, but trying to keep the hydrocarbons under control.
00:37:18Yep.
00:37:19So we could have that, that glorious making of popcorn,
00:37:24but they improved the crank.
00:37:26And so the stroke went back down for the RZ three 50.
00:37:30Well, the thing that, um, was always a weakness with the modular engines that began in, uh,
00:37:38the early seventies was that there were four crankshaft flywheels, two crank pins.
00:37:46There were separate pieces like this.
00:37:48So there was a press fit on both ends and the two inner flywheels went together by one
00:37:56of them, having a solid shaft that fitted inside of a tube on the other.
00:38:01You press those things together, seven tons and they would break, would break the smaller shaft.
00:38:10So they made a bigger shaft and a bigger tube for the racing bikes, the TZs.
00:38:18And, uh, then they had a modified bearing to make, to accommodate the larger tube.
00:38:24And that stopped that breaking.
00:38:25But that meant that there was one flywheel that had two holes in it.
00:38:30It had one for the shaft going through the center and one for the crank pin.
00:38:35And they were as close together as the holes in a figure eight.
00:38:39Now you'd expect it to break between there, but it didn't.
00:38:43It, it broke in all sorts of other ways as if that was forbidden.
00:38:49Cracks would come and wander through the thing.
00:38:52And the most wonderful result was that somebody's flywheel would come in half,
00:38:58would open up, let's say 10,000 RPM, like a pair of steel brake shoes,
00:39:03and wipe out the crankshaft crankcases so badly.
00:39:09So on TZ 750, where the crankcases were a thousand dollars,
00:39:14uh, we learned to, uh, shot peen the areas where the cracks might form
00:39:20and to inspect by means of magnetic particles, um, look for cracks in all those crankshaft parts.
00:39:29So that's what happened as life progressed.
00:39:32We kept getting more power from the engines.
00:39:35The same old parts were running out of breath.
00:39:39So when they did the RZ, they made the two inner flywheels
00:39:44and the shaft connecting them into one piece.
00:39:49So that meant, and then they made the outer flywheels and the crank pins in one piece.
00:39:56So now there are only two press fits and there's no flywheel with two, two holes in it.
00:40:04And that made the crankshaft a lot, uh, more resistant to failure at prolonged high RPM.
00:40:11Unfortunately, of course, 84, that was when the two-stroke thing was,
00:40:16was, it really ended.
00:40:18No more street two-strokes.
00:40:21And there could have been a future for the two-stroke engine
00:40:26if they'd had all of that tricky direct cylinder injection.
00:40:31Well, if only the Bimota V-2A would have worked out.
00:40:34The 500 twin two-stroke, boy, that had some problems.
00:40:37But, um, we thought it, we thought Bimota was bringing us a return to the glory days,
00:40:43but it's, it's injection system didn't work.
00:40:46It didn't work.
00:40:47Just plain didn't work.
00:40:49Just didn't run.
00:40:50But of course, uh, making motorcycles is a business
00:40:56and there might be honor in carrying on with the two-stroke idea,
00:41:01no matter what the cost, but businesses can't operate that way.
00:41:06So, um, everyone looked at the options and they said,
00:41:12let the car industry do all the research for four-stroke emissions control,
00:41:17and we'll buy it over the counter and apply it to our four-stroke future.
00:41:23And the two-stroke thing just ceased to exist all over with,
00:41:28except that crazy folk like ourselves harbor illicit parts and even whole motorcycles.
00:41:40Of course, it's legal to ride them because they're grandfathered in.
00:41:45But, uh, generally speaking, the difference between a two-stroke and a four-stroke,
00:41:51four-stroke makes, burns roughly a half a pound of fuel to make one horsepower for one hour.
00:41:58And the two-stroke, nicely tuned one, more like 0.65 pounds.
00:42:05So, uh, an extra 30% of fuel is passing through the two-stroke
00:42:13and out into the open air where the EPA can detect it.
00:42:19And that had no future.
00:42:23You said after porting the cylinder on mine, you said, well,
00:42:27you know, you'll find that at low RPM, you'll get pretty terrible fuel mileage
00:42:31because it's just all getting chucked out the pipe.
00:42:35You're not getting any energy from it.
00:42:37It's just getting, just basically migrating through your, uh,
00:42:41crankcases and out the pipes.
00:42:42And away you went.
00:42:43Well, and that's why, uh, the, the later two-stroke twins had the eyelids in the exhaust.
00:42:52Because if you were building an engine to operate at 4,000 RPM,
00:42:56it would have quite low exhaust ports.
00:42:59And if you wanted to operate at say from nine to 12, you would have taller exhaust ports.
00:43:08And so the eyelid is simply there to, to be, to open the exhaust at the
00:43:14point that is appropriate to the RPM the engine is making at that moment.
00:43:18And there was too little too late.
00:43:22They were, it was a lovely device.
00:43:25There were other resonators were added to the exhaust, all sorts of things, water injection.
00:43:31But, uh, two strokes were over with because it would be another
00:43:3710 years really before, uh, direct injection showed that it could have been, uh, done.
00:43:46But, uh, by that time, four strokes are in production everywhere.
00:43:49People love them.
00:43:51And that's how it is to this day.
00:43:54What's the practical RPM limit on a two-stroke like an RD?
00:43:59Well, the RPM limit is quite low compared with four strokes because, uh, the process of passing
00:44:11the fuel air mixture from one volume to another doesn't lend itself to 20,000 RPM operation.
00:44:22So, uh, when they, the 125 CC cylinder was the, the module of Grand Prix racing for many years.
00:44:33So the 125 class had one cylinder, the 250 class had two and the 500 class had four.
00:44:40And I think Honda got their 500 to run, uh, between nine something and nearly 13,000 RPM.
00:44:51And I think the Alhaz ran a little short of that, but the thing was, uh, a two-stroke
00:45:01fires twice as often as a four-stroke and toward the end of their development, two-strokes were
00:45:07able to fill the cylinder at least as well as a fully developed racing four-stroke, which meant
00:45:16that a 125 single at the end of the two-stroke era was making over 55 horsepower.
00:45:26And the two fifties in 1994, Honda set as a goal,
00:45:31okay, fellas, this year, our two fifties are going to hit 100 horsepower.
00:45:38And the five hundreds, it was a tricky thing because
00:45:42with, uh, the power that they were making in the, uh, nineties, it went from like 160 horsepower to
00:45:49190, even though the fuel was being de-leaded, which meant the compression ratio had to come down.
00:45:57Uh, five hundreds were tricky to ride because they had enough power to break the tire loose
00:46:03a lot easier than a 250 and especially a 125. So the power was softer when the sidecar guys
00:46:11began to use Yamaha four cylinder, five hundreds, they wanted two 50 cylinders because they made
00:46:18more power than 500 cylinders. They were just a little more radical, but, uh, then there was a
00:46:26company, a couple of outfits built five hundreds toward the end of the two-stroke era that made a
00:46:34lot more power than the factory, uh, the Japanese factory five hundreds, but they were
00:46:43not rideable. They could go down the straightaway at a tremendous rate of speed, but they just
00:46:50stayed in the corners. And what the Japanese had done supremely well was to,
00:46:58to control the power valve or other exhaust device electronically so that they could say,
00:47:05oh, well, we use this program for this racetrack and we use this profile for this other racetrack.
00:47:14And, uh, there was the whole business with big bang. There were all these things happening.
00:47:23Um, and it was a fast moving time, but in the end, 500 two-stroke lap times stagnated
00:47:32because they couldn't feed power from zero. A four stroke, you can start to turn the throttle
00:47:41in the middle of a corner. If the thing is docile enough and it will feed from zero so that you can
00:47:48accelerate as the motorcycle makes more traction available as it rises from full lean to upright.
00:47:57So you're adding power during that time. Four stroke allowed you to do that very smoothly.
00:48:03The two-stroke, despite all these civilizing measures that were applied to it, uh, remained
00:48:12hard to get off the bottom so that you had Mick Doohan riding in that,
00:48:19it was once called a defensive style with his inside shoulder turned forward, his body offset
00:48:25to the inside of the corner and lifting the motorcycle up so that he could withstand the
00:48:36hit when the engine eight stroke, four stroked, and then two stroked and away you go.
00:48:43And, uh, he became good enough at that, that he won five straight 500 championships.
00:48:50And the reason that I've digressed here is that there was always a close relationship with what,
00:48:56between what was going on on the racetrack and what was happening in production two strokes,
00:49:02including motocross. Lots of motocrossers were built with power band broadening, uh,
00:49:09ideas built into them so that it was a, it was a kind of unity. It seemed like,
00:49:16like two stroke was another country. And if you were, uh, in for a, for an RD 500 or RD 350,
00:49:26you were in a group in which you could find Mick Doohan and you were dealing with many of
00:49:33the same problems that he encountered trying to go fast on the 500. So it was a, it was
00:49:43when two strokes first arrived, there was that year when, when, uh, Yamaha 350 twins
00:49:50finished second and third in the Daytona 200. And at that time, the AMA had been contemplating
00:49:58a 350 maximum displacement because as race sanctioning bodies always do, they were
00:50:07pulling their whiskers and say, Oh, it's too fast, too dangerous. Oh, think of the liability.
00:50:13And those two, three fifties in second and third up, forget that idea. We're going with seven 50
00:50:22and that's what they did. So two strokes were always there poking and pinching and offering a
00:50:30low cost violence solution. And I enjoyed the daylights out of it. It was a good time
00:50:39to have a die grinder and a gas welder. Or if you lived in California, of course,
00:50:45every garage had a TIG welder in it. Well, I cracked up because you said something about,
00:50:52you know, the power coming on, on a, you know, TZ 750 or maybe it was the RD, but after it was
00:50:59ported and you said, well, you know, once you, whatever you said, once you got to 9,000 time
00:51:03to cut wood way and a way it goes, it's, it's a thing of beauty. You know, if you want to just
00:51:09rattle down the road, short shifting and so forth, you know, your excess six 50 is a,
00:51:15is a great way to roll. Right. You know, like tip, tip, tip, tip, you know, as you say,
00:51:19you can pick up, pick up from zero nice and smoothly and you can short shift and you can
00:51:25kind of pitter patter down the road. But you know, two strokes aren't, aren't as
00:51:29amenable to that. They can be made to run like that. But as soon as you put a little sizzle into
00:51:35them, away you go. That bottom end, forget about it. Yes. It's like a Saturn five rocket. There's
00:51:41no part throttle when you take off, there is part throttle. Once they, they get up to a certain
00:51:48altitude, they had to throttle back. They called it max Q, which is the greatest resistance from
00:51:54the atmosphere. But like a Saturn five, a two stroke required a full commitment from,
00:52:04from the passengers because it was a, it was an unmanageable application of fire in a closely
00:52:14confined space. And it, it acquired all of this complexity, the complexity having to do with how
00:52:25the streams enter the cylinder, how they loop up to the cylinder head and down to the exhaust port,
00:52:32just as the piston is about to close the exhaust. All of that took a tremendous amount of thought
00:52:39and repetitive testing. And it did its job and it was over with. And now it's just history.
00:52:47It has no application, but the two stroke principle lives on in the gigantic engines
00:52:54that power world trade because every one of those container ships has something like
00:52:59a 100,000 horsepower, two stroke diesel, two stories high, driving a 30 foot propeller
00:53:09directly. The engines, the power band, 80 RPM, eight zero. So,
00:53:22and the reason that it's in that job is that it is the packs, the density of power
00:53:28that allows the ship to carry the maximum amount of cargo. It's business. And of course, when
00:53:36two strokes became bad business, they were no business at all. That's where we are today. I
00:53:42mean, there are still people playing with the principle and there have been a few low production,
00:53:47direct injection or transfer port injected engines. And you have to admire their persistence.
00:53:56But the problem is that a small industry cannot as easily afford the pioneering,
00:54:05the endless testing that is required to meet EPA. And when it proves not to be easy,
00:54:15it doesn't happen. Well, 302 strokes transfer port injected or no are still the greatest
00:54:23off-road bikes. All the torque, all the lightness, the power you want when you want it.
00:54:28Sure.
00:54:29Great, great immediate response. They're still doing those KTM and company are still making the
00:54:34302 strokes in there. They're magnificent. I wanted to talk to you. So when I was there years
00:54:41ago and we were out in the shop and I said, well, it was time for dinner. We were going in and
00:54:47there was the porcelain line pot with some stew in it or something. And
00:54:52I said, well, let's talk about transfer, the theory of transfer ports and how all that works.
00:54:58And you said, oh God, we'll be up all night. And I said, yeah, maybe that's a lot to tackle.
00:55:07However, how did you, how did you figure it out? Were you looking at the witness,
00:55:16the combustion, the piston crown? Did the piston crown tell you things?
00:55:21There's a bunch of evidence that you can gather. And the piston crown is one of them. Ideally,
00:55:28you would want the piston crown to be the usual sort of soft light gray and with hardly a mark.
00:55:38But if you're a bit rich, there will be deposits on the piston crown that show where fuel has
00:55:46partially carbonized on contact with the hot aluminum. And so you can get an idea of things
00:55:53are going in the direction of the port appears to be pointed.
00:55:58But one of the basic problems with these engines is that, and it is a problem with the RD, is that
00:56:09there are 180 degree crankshafts. So you would think vertical shaking forces
00:56:17is self-canceling. That would only be true if the two pistons were somehow moving this way,
00:56:25as they do in a BMW, boxer motion, but they're offset. And because they're offset,
00:56:33the crankshaft rocks from side to side. And in all of Yamaha's early parallel twins,
00:56:40this broke the frame sooner or later. So what they did was they wanted,
00:56:46they knew that this rocking motion was going to break things.
00:56:50So they pushed the cylinders as close together as the transfer ports would allow.
00:56:57And the result was transfer ports that did not resemble the two cup handles on a mug,
00:57:07but which resembled an elevator that goes up to the floor and the door opens and you go out at
00:57:12right angles to the elevator shaft. And air does not like to go around a sharp right angle like
00:57:19that, and it won't do it. In an air conditioner ducts, they put little guide vanes in the middle
00:57:26of the duct to sort of help things out. But if you feel around in there with an impact probe
00:57:35connected to a sensitive gauge, you can map the outflow from the transfer ports by
00:57:41setting the cylinder down on a blower box, blowing air through the transfers, and you
00:57:47map it out and you find out only the upper two thirds, or maybe even as little as one half
00:57:54of the transfer windows are flowing anything. Because the air going around such a sharp corner
00:58:03goes out to the outside, and it does not follow the much sharper corner on the inside.
00:58:08Same as the four stroke short side problem. How are you going to make the air turn down
00:58:14the near side of the valve? So what Yamaha eventually did was, you have a parallel twin
00:58:21like this. They made a 90 degree v-twin like this, which allowed the cylinders to be
00:58:30spaced a little bit closer, but most of all it made room for those cup handle transfer ducts.
00:58:38Nice graceful ones. And Jan Thiel, who did so much for European two strokes in the day,
00:58:48he and his friends built from zero a 50cc racer that won the world championship.
00:58:57So those fellows learned a good deal. And Jan Thiel said, my engines really started to make
00:59:06some power once we got those gracefully curved transfer ports. And that was a real problem on
00:59:16all of those parallel twins where the cylinders were crowded together so that the transfer
00:59:20ducts had very little room. Suzuki helped that problem a little bit with their two transfer,
00:59:28like their 750 so-called water buffalo. They rotated the cylinders. This is looking down
00:59:35on them from above so that the transfer ports were next to one another rather than being crammed
00:59:41together. And that's the engine that Gary Nixon, of which Gary Nixon once said,
00:59:49probably a pretty good little engine. It wasn't a damn hard to ride.
00:59:54It had, with due respect to Gordon Jannings, who said smooth, broad power bands come from
01:00:08exhaust pipes with gentle tapers. Well, those 750 Suzuki's had gentle tapers, but they had a
01:00:17violent power band that was like on and off. And that's why Gary said that,
01:00:22if it weren't so damn hard to ride. And so those V-twins were a step forward in 250s,
01:00:36but they didn't arrive until it was time for the two-stroke to exit stage left.
01:00:44So there are a few of them, the productionized ones around. Good luck finding pistons,
01:00:53but it was fun while it lasted. It was, still is a little bit for a few of us. And of course,
01:00:59we have to remember that two-strokes began to appear to annoy people. In 1970, Ginger Molloy
01:01:10was second in the world championship on a Kawasaki H1R, a triple production racer
01:01:19that he had bought for $1,500. And there was Agostini on high.
01:01:30Count Augusta cannot be happy about this. Yeah. And there was a good old Ginger,
01:01:37tricky, crafty old guy, wonderful character. Arturo Mani, who are these pirates?
01:01:45Yes. But it kept coming. It kept coming. And Suzuki won the 50cc championship. That was the
01:01:55first two-stroke win of a world championship. Then the 125 and the 250. And by 1975, every class,
01:02:05including sidecar, was won by a two-stroke. And that's why the English and the Australian
01:02:13four-stroke folk referred to that as the forgotten era, because they wish they could forget it.
01:02:21And in 1975, things were just starting. Two-stroke 500s were making 90 horsepower,
01:02:32100 horsepower. And it just took off from there. And the reason the four-strokes didn't have a
01:02:38chance was that it probably cost between 10 and 100 times more to get five extra horsepower by
01:02:46four-stroke than by two-stroke. Because with the two-stroke, you just had the people in the
01:02:51dyno room working. And periodically, they'd phone, hey, boss, we got something. We got something.
01:02:59And Honda liked to make out that, well, we have this powerful computer which answers
01:03:06all our questions. But in fact, the way the two-stroke horsepower was developed is there
01:03:11were two drunk fellows in the basement of, I don't know whether it was HRC. It might have
01:03:17been too early for that. But they worked in the basement of the big research area.
01:03:22And they had a system of exhaust pipe cones that could quickly be snapped together to make
01:03:28different shapes that would give them some idea within minutes. And they're in there with
01:03:37die grinders. They're doing exactly what the RD350 guys were doing. They were finding their way,
01:03:46cut and try. It was wonderful. And it was wonderful to hear that that's how it came
01:03:54about. And what would happen is that the engineers would look at the trend lines,
01:03:59oh, well, transfer ports are moving in this direction. We'll put a dotted line that shows
01:04:05what will be next year. And then the prototype would be put on one of those little wheeled
01:04:12carts. And a technician wearing a company hat would wheel it to the dino room. And those two
01:04:17guys would look at the thing carefully. And they would go,
01:04:24Pepto-Bismol and Motrin, please. And they would get busy because they knew that the final
01:04:33horsepower had to come from cut and try. Nobody wanted to know what it was that these fellows
01:04:39were doing in the basement, but they wanted the results. And that's the way it worked.
01:04:46And I was therefore so delighted when I listened to conversation from a member of the original SR71
01:04:58design group who said, when we flew the prototype, we saw that one of the spars in the wing
01:05:07was loaded almost to yield point. And we thought, oh, we will bend the front of the wing down like
01:05:16this. So they made one like that. And it was a big improvement. The airplane flew better.
01:05:24The stress was more equally distributed among the several spars, which a delta wing always has.
01:05:30And it was cut and try. It was not gigantic computers with 3,000 processors and artificial
01:05:42intelligence. It was real intelligence, actual human intelligence. You know,
01:05:50this cylinder reminds me of something I saw three years ago. Bud Axelrod worked this way.
01:05:56Bud Axelrod would get up in the morning, go to his shop, and start testing exhaust pipes.
01:06:05That one's bad. That one's bad. That one's bad. This one has some promise. That one's bad.
01:06:13Persistence. Well, when Cal Carruthers kind of came out of retirement and was working on
01:06:18jet ski, you know, watercraft race motors, big three-cylinder two-strokes,
01:06:25he just made pipes and he'd cut them, make them shorter, do that, do this, do that. And they were
01:06:30like, dang, this guy is making power. It was pretty cool. It was a pretty neat time to know
01:06:37Cal and hear about that stuff. Because when Cal and Don Vesco had that original partnership in 1971,
01:06:47Cal told me years later, of course, you wouldn't have dared to speak to Cal in his years of
01:06:55mastery because, of course, he was surrounded by phalanx of people like Pete Schick,
01:07:03who would look at you as if you were a worm. May he rest in peace. Cal said,
01:07:13Cal said, Vesco had this dreadful little dynamometer off in a corner. And I went and
01:07:22poked around and kind of cleaned it up and got things working. And he said, I built a single
01:07:27cylinder test engine out of discarded crankcase. Warranty parts are a huge thing in racing
01:07:35development where you're starting with production parts. And he said, I got the engine up and
01:07:44running and I got it so that I could measure the torque. And I sort of knew my way around and I
01:07:51started finding things out. Those were his words. I started finding things out.
01:07:58And roughly what he found out was the new TZ250 comes and its compression is really dismal. It's
01:08:07made to run on wartime red gas, the stuff they put in jeeps. And the exhaust port was,
01:08:17what's it doing way down there? So he would adjust the exhaust port dimensions to what he
01:08:25thought would work. He raised the compression ratio and he found that raising a compression ratio
01:08:34brought the RPM of peak power down. Because if you're taking more energy out on the piston crown
01:08:40by raising the compression, there's less energy going out the exhaust port. So the temperature
01:08:45is lower and the pipe resonates at a lower frequency. So he took 20 millimeters out of
01:08:55the header pipe or 20 millimeters out of the header pipe and five or seven millimeters out
01:09:01of the center section. He tried stuff and he got power. And he found that he found his way around.
01:09:12He wasn't a two-stroke guy to begin with. In 69, he got some of his world championship points
01:09:19on a Yamaha TD2 and some on a Benelli four-stroke. So he found his own way.
01:09:28Now, Cal is a clever man, probably much better than average at finding his own way with the dyno
01:09:36and all those many variables, but he got hold of it. And the Japanese regarded Cal-san as an oracle
01:09:46of excellent information. And they weren't too sure how he went about getting it,
01:09:53especially since he didn't attend Tokyo University.
01:09:57But as Mr. Yoshida, who was our technician at Kawasaki, once said, necessary many testing.
01:10:09So that'll be the next podcast. We'll talk about pipe design or something.
01:10:15We can talk about some of that stuff. And you also said
01:10:19that you wanted at some point to talk about favorite tools.
01:10:23Yes.
01:10:24And we all have favorites and each one of them has a story. So
01:10:34as in consideration of tomorrow's breakfast, there's something to look forward to.
01:10:39That's right. Favorite tools. We'll talk about maybe two-stroke exhaust pipe design
01:10:46and all the things working on that. And we'd already discussed doing an entire podcast on
01:10:52the NSR500 evolution, basically during the McDoon years and the changes that they made
01:10:57from Big Bang to Screamer and all that. So we'll hit that as well. We've had some
01:11:02great suggestions in comments. We thank you for listening. This episode, as ever,
01:11:09is brought to you by Octane Lending, our parent company. There's a prequal flex link
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01:11:27We appreciate you listening and we will catch you next Wednesday.
01:11:32You bet.