New Yamaha RD350?!

[Johnny Monsoon]

Did you know there were two stroke cars? Suzuki even built two stroke "jeeps", 4x4s with little two strokes in 'em. They were kinda cute, very quite, and weird to listen to. I wanted one. There were a few around, never actually imported to the US officially, sorta grey market. Suzuki place in Clute, Champion Suzuki (they're gone now) had one and I saw one at the IHOP in College Station once, guy got in and fired it up. A TWO STROKE!

http://www.off-road.com/trucks4x4/article/articleDetail.jsp?id=277664

Complicated as an XX?!? That's one of the most straightforward bikes/engines ever!

And yeah, I was thinking about the 2smoke cars; in fact, in Europe they were quite popular early in the automotive industry because they were cheaper to produce (not for any other reason). However, just like with bikes, the 2 stroke was phased out of existence, largely, because they were loud, they have garbage economy, they're very limited in application (works best at 100% duty cycle) and they were anything but reliable.

They still make some. Japan sells them. They are sold with the intent that they will not last more than two years (words directly from the sales points). The cost to repair is generally the cost to replace (or so close that it becomes indistinguishable) and you never see any on the road more than a year or two old, and you ONLY see them in micro-cars that are incapable and illegal to operate on the highway system there (which has a top speed of 45mph over 90% of it's path).

 

[Jack Giesecke]

Complicated as an XX?!? That's one of the most straightforward bikes/engines ever!

And yeah, I was thinking about the 2smoke cars; in fact, in Europe they were quite popular early in the automotive industry because they were cheaper to produce (not for any other reason). However, just like with bikes, the 2 stroke was phased out of existence, largely, because they were loud, they have garbage economy, they're very limited in application (works best at 100% duty cycle) and they were anything but reliable.

They still make some. Japan sells them. They are sold with the intent that they will not last more than two years (words directly from the sales points). The cost to repair is generally the cost to replace (or so close that it becomes indistinguishable) and you never see any on the road more than a year or two old, and you ONLY see them in micro-cars that are incapable and illegal to operate on the highway system there (which has a top speed of 45mph over 90% of it's path).

I tell ya what, you change rings in that XX and I'll change 'em in a water buffalo and we'll see who'd finished first. DOHC under bucket shimmed 16 valve, right? Probably has a base gasket, which is way old school. Most modern sport bikes don't now days. Hec,, I'll beat ya with a Z1 Kawasaki or Suzuki GS! I wore the rings flat out at 22K miles on a GS750, BTW. At the time, early 80s, things cost me $100 for the parts. OUCH! 25 bucks a ring set. At the time, I could buy a piston kit for that for my TZ250 motor.

That little Suzuki 4x4 was anything BUT loud. It was about as loud as my Toyota Echo, only made a strange sounding hum. The reason they never brought 'em here is they were underpowered what with a max engine size of 550ccs in the last models and a top speed of 60 mph. They were built to fit into a Japanese CC limit for the home market.

I remember the first Honda cars, too. Guy that ran the Yamaha shop in College station had a couple, one a parts car. They had an air cooled four stroke motorcycle engine in 'em, 650cc. They were also built for the Japanese home market to fit a specified CC limit. They didn't exactly accelerate hard or have a great top speed, either. They were TINY, but kinda neat and I always thought they'd be fun and practical.was making a buck sixty an hour.

 

[Jack Giesecke]

I'm w/ Jack, you don't have a clue ex. for the limited world of non-cutting edge two and four strokes that you have experience w/. Jack's preferences aside, I wouldn't want a two stroke street bike, and won't ever go high mileage on any bike. I'd be surprised if ANY MX bike ever got close to 75K miles...but at any rate, 2 stroke top ends are designed to wear out. No big deal, $100 and a couple of hours...less time and money than I'll spend over that period than changing oil in the 450.

Here's some food for thought:
http://twostrokemilitia.jfn3.com/index.html

http://twostrokemotocross.com/2008/08/yz250-vs-yzf250-by-mxa/

It's not that they are "designed to wear out", just that the large exhaust port and transfers of a high performance two stroke, racing two stroke, are hard on rings. Also, the high RPMs of either motor causes ring flutter and wear, be it four or two stroke. Back in the day of the piston port TZ, the intake ports would wear a litle smile on the back of the skirt and the pistons had to be swapped after 300 racing miles, caused by high output tuning, not by being "designed to wear out". Mildly tuned motorcycle engines or car engines of two stroke design had none of these top end problems. The water cooled ones were much easier on parts. If you can fine it, "Two Stroke Tuner's Handbook" by Gordon Jennings is a must read for the two stroke guy to understand the intracacies of the engine.

I think the RZ350s were the ultimate in compromise as street bikes. Top ends on these things were water cooled and would run many thousands of miles with no maintenance. They produced mid 40s horsepower to about 50 bone stock and a set of expansion chambers and some porting could get 'em up to near 70 at the expense of reliability, longevity of parts. That's always a compromise, not a part of being a two stroke. SV650s producing much more than 80 horsepower in race trip can become grenades.

RDs with their air cooling and 35 hp output could run 35-40K on a top end. The RZ made more horsepower and could push top end maintenance by double. Not many saw the street and unmodified, though. Most got number plates strapped on 'em. They sure made sweet street bikes and with a good set of pipes, would turn up around 50 hp reliably and weighed less when you chunked those heavy catalytic converters. The RZs were sweet. Wish I'd been in a position to buy one, then, but I got laied off in 82 and rehired at about 4.50 less an hour than I'd been making and then had to sell my house and move down here. Money was short at the time. It was a recession that makes today's fear mongers look a little comical to me. Great depression indeed! But, that's another subject.

Yes, two stroke dirt bikes have many times more advantages than do the street versions. That's why they've dominated racing so long and only have been pushed out by giving four strokes a double displacement advantage. Four strokes are getting lighter, but they're still pigs by comparison to the two strokes. You'll find most of the "extreme" guys, the stunter types, on two strokes for that reason, easier to toss around less weight. Greenpeacer's are running two strokes out of production, the tree huggers, salad eaters, not any advantages a four stroke has. In racing, a four stroke cannot compete on an even playing field, cc for cc, just ain't got it. Therefore, the rules have been changed. for the four stroke lovers.

Be careful, though. The tree hugger types don't like internal combustion, let alone two strokes. Won't be long and motorcycles and motorcycle racing will be a thing of the past. Oh, there might be XXs, but they'll have electric motors driven by batteries. BUT, they'll be quiet! D and D won't be able to make pipes for 'em. Gonna be great at a GP, eh? Whoosh.....whoosh....whoosh....at least you'll be able to hear the announcer over the "whoosh."

 

[Johnny Monsoon]

Be careful, though. The tree hugger types don't like internal combustion, let alone two strokes. Won't be long and motorcycles and motorcycle racing will be a thing of the past. Oh, there might be XXs, but they'll have electric motors driven by batteries. BUT, they'll be quiet! D and D won't be able to make pipes for 'em. Gonna be great at a GP, eh? Whoosh.....whoosh....whoosh....at least you'll be able to hear the announcer over the "whoosh."

Hey, my B12 had a D&D! I'm not sure I'd want 'em on an XX though...

I wonder if the issues the 4 strokes are having (reliability in MX racing; oddly the SM world doesn't have those issues) isn't more related to the 2-stroke theory of racing vs, a different approach vs. 4 stroke. After all, you're doing a lot more throttle pinning and clutch feathering on a 2 stroke than you would on a 4 stroke. But, if I've come up on 2 strokes and jump right on a 4 stroke and try to ride it the same, I'm gonna have problems.

 

[Jack Giesecke]

Hey, my B12 had a D&D! I'm not sure I'd want 'em on an XX though...

I wonder if the issues the 4 strokes are having (reliability in MX racing; oddly the SM world doesn't have those issues) isn't more related to the 2-stroke theory of racing vs, a different approach vs. 4 stroke. After all, you're doing a lot more throttle pinning and clutch feathering on a 2 stroke than you would on a 4 stroke. But, if I've come up on 2 strokes and jump right on a 4 stroke and try to ride it the same, I'm gonna have problems.

Reliability is a function of output vs displacement. It really doesn't matter if the race engine is four stroke or two. If you have a 500cc to 600cc thumper putting out 80 horsepower (Ducati supermono) or a 450cc thumper putting out 55-60 horsepower (common supercross engines), you are doing it with high rpm. Add to that the fact that you must design parts to take the stress of a moto or practice session (you can swap motors in the pit) and, yeah, they'll be high maintenance. Plus, reciprocating parts in a four stroke must be light since weight causes inertia which causes stress on reciprocating parts. You'll notice 24 hour endurance motors tend to be slower. They're tuned more mild to hold up for the race. They can't be stressed to the levels of a bike that runs a 10 lap sprint at most.

You can't get away from high maintenance in a race engine, period, not if it's built to win races. The YZF426s were having all kinds of crank failure problems when they came out, when used for SM or road racing . They got parts light for MX and they held up where you weren't in the throttle at redline all that much on an MX track. On the road courses like TWS, they blew up when pinned at redline for the length of a straight away. My KX, OTOH, did just fine at 11,500 rpm down the front straight of TWS. It won a few races there and ran well even against the GP 80s.

Only a couple of guys could consistently beat it and they had LOTS of money and tuning in their engines and correspondingly more maintenance between races. But, hey, they were excellent riders, too. Weren't all money, but to dominate at big tracks, you have to be living on the edge with engine tuning. I heard tell Tyler's 80 made something like 27 horsepower.... Being 80 lbs and blazing fast rider didn't hurt, either, just sayin'. His dad owns a motorcycle shop and used to be partners in K&N, the filter company, so they could afford the PM between races and the high dollar tuning work.

Now, there are the CRF150s that dominate that class, both CMRA and TMGP. The 80s run behind them. It's not even close. I can handle an average rider on one on a kart track, but the average guys don't spend that kind of money. Last time I went to a TMGP race, Phillip (super fast) Fisher was dominating everyone on a CRF. The 80s didn't stand a chance. It's a 150cc water cooled short stroke 4 valve DOHC racer. It costs more to buy and more to race, but hey, even in minis, costs go up. But, what I like about two strokes in racing is they're more po boy friendly. Building one isn't as expensive to do. If you can't afford the upkeep ona 27 hp motor, hey, build a 20 horsepower motor and ride harder. Stock 80s are around 18 ponies and CRF150Rs turn around 23 out of the crate and are close to 5000 bucks.

 

[Johnny Monsoon]

Reliability is a function of output vs displacement. It really doesn't matter if the race engine is four stroke or two. If you have a 500cc to 600cc thumper putting out 80 horsepower (Ducati supermono) or a 450cc thumper putting out 55-60 horsepower (common supercross engines), you are doing it with high rpm. Add to that the fact that you must design parts to take the stress of a moto or practice session (you can swap motors in the pit) and, yeah, they'll be high maintenance. Plus, reciprocating parts in a four stroke must be light since weight causes inertia which causes stress on reciprocating parts. You'll notice 24 hour endurance motors tend to be slower. They're tuned more mild to hold up for the race. They can't be stressed to the levels of a bike that runs a 10 lap sprint at most.

You can't get away from high maintenance in a race engine, period, not if it's built to win races. The YZF426s were having all kinds of crank failure problems when they came out, when used for SM or road racing . They got parts light for MX and they held up where you weren't in the throttle at redline all that much on an MX track. On the road courses like TWS, they blew up when pinned at redline for the length of a straight away. My KX, OTOH, did just fine at 11,500 rpm down the front straight of TWS. It won a few races there and ran well even against the GP 80s.

Only a couple of guys could consistently beat it and they had LOTS of money and tuning in their engines and correspondingly more maintenance between races. But, hey, they were excellent riders, too. Weren't all money, but to dominate at big tracks, you have to be living on the edge with engine tuning. I heard tell Tyler's 80 made something like 27 horsepower.... Being 80 lbs and blazing fast rider didn't hurt, either, just sayin'. His dad owns a motorcycle shop and used to be partners in K&N, the filter company, so they could afford the PM between races and the high dollar tuning work.

Now, there are the CRF150s that dominate that class, both CMRA and TMGP. The 80s run behind them. It's not even close. I can handle an average rider on one on a kart track, but the average guys don't spend that kind of money. Last time I went to a TMGP race, Phillip (super fast) Fisher was dominating everyone on a CRF. The 80s didn't stand a chance. It's a 150cc water cooled short stroke 4 valve DOHC racer. It costs more to buy and more to race, but hey, even in minis, costs go up. But, what I like about two strokes in racing is they're more po boy friendly. Building one isn't as expensive to do. If you can't afford the upkeep ona 27 hp motor, hey, build a 20 horsepower motor and ride harder. Stock 80s are around 18 ponies and CRF150Rs turn around 23 out of the crate and are close to 5000 bucks.

Who's talkin' about race engines? Still, if we're talking performance, let's quantify. I can ride a KLR around a track for 75K with no problem. Won't get airborne or pull freestyle stunts with it, but it'll make it just fine. May not do it as fast as a two stroke MX bike, bu it'll do it. I'd wager that it'll do it one helluva lot longer, even if neither one is 'racing'. Performance, literally is just a measure of a characteristic of something. Reliability can be a measure of performance; and is generally a pretty good one.

Debate started when 2 strokes were noted as not being on Honda's list.

I said I was happy becasue 2 strokes stink, they're loud, and they don't last like a 4 stroke (for road or otherwise, and generally becasue they aren't as highly stressed). 2 strokes fire twice as often as 4 strokes do, so it should be no surprise to anyone that they suffer from fatigue faster.

A 2 stroker isn't a superior engine to a 4 stroke. It's a different engine.

 

[bmcdonau]

Who's talkin' about race engines? Still, if we're talking performance, let's quantify. I can ride a KLR around a track for 75K with no problem. Won't get airborne or pull freestyle stunts with it, but it'll make it just fine. May not do it as fast as a two stroke MX bike, bu it'll do it. I'd wager that it'll do it one helluva lot longer, even if neither one is 'racing'. Performance, literally is just a measure of a characteristic of something. Reliability can be a measure of performance; and is generally a pretty good one.

Debate started when 2 strokes were noted as not being on Honda's list.

I said I was happy becasue 2 strokes stink, they're loud, and they don't last like a 4 stroke (for road or otherwise, and generally becasue they aren't as highly stressed). 2 strokes fire twice as often as 4 strokes do, so it should be no surprise to anyone that they suffer from fatigue faster.

A 2 stroker isn't a superior engine to a 4 stroke. It's a different engine.

All this is moot in todays environment since you can't make a conventional two stroke engine of any usable size that will pass US or Euro air quality specs. Lotus is working on a fuel injected two stroke that shows some promise. I think one of the Japanese companies was looking at the same concept back in the early 90s, but gave it up when they stopped racing two stroke street bikes. I don't remember exactly, but the valves work sorta like the Yamaha YPVS did in the 80's bikes.

 

[Jack Giesecke]

Who's talkin' about race engines? Still, if we're talking performance, let's quantify. I can ride a KLR around a track for 75K with no problem. Won't get airborne or pull freestyle stunts with it, but it'll make it just fine. May not do it as fast as a two stroke MX bike, bu it'll do it. I'd wager that it'll do it one helluva lot longer, even if neither one is 'racing'. Performance, literally is just a measure of a characteristic of something. Reliability can be a measure of performance; and is generally a pretty good one.

We were talkin' MXers, right? Chris S was, anyway. If you wanna WIN, you won't be on a KLR. I'll be takin' the checkers when you're completing laps one, if a bike or two don't rear end you in the process. We used to call such guys "rolling chicanes".

Debate started when 2 strokes were noted as not being on Honda's list.

I said I was happy becasue 2 strokes stink, they're loud, and they don't last like a 4 stroke (for road or otherwise, and generally becasue they aren't as highly stressed). 2 strokes fire twice as often as 4 strokes do, so it should be no surprise to anyone that they suffer from fatigue faster.

A 2 stroker isn't a superior engine to a 4 stroke. It's a different engine.

It is a superior design for racing. On the street and in street tune, it can be just as nice a ride as any four stroke, the G750 proved that, two stroke GoldWing. The RD400 was perhaps the perfect middle weight street bike, too. It was mild mannered, yet could embarrass a lot of bigger bikes, especially on a curvy road. In fact, in a Cycle World test, it was declared "A horn away from the perfect motorcycle". They didn't like the weak horn.

 

[Chris S]

I suspect he's never been on a MX track. I'd worry about being run over or landed on riding a KLR for MX! I'm beginning to wonder if he's ever even heard a modern MX bike, since I couldn't barely hear my old YZ250 or current 300 XC-W over the average CRZ/RMZ/KXF/YZF.

 

[Jack Giesecke]

All this is moot in todays environment since you can't make a conventional two stroke engine of any usable size that will pass US or Euro air quality specs. Lotus is working on a fuel injected two stroke that shows some promise. I think one of the Japanese companies was looking at the same concept back in the early 90s, but gave it up when they stopped racing two stroke street bikes. I don't remember exactly, but the valves work sorta like the Yamaha YPVS did in the 80's bikes.

Yeah, I know, but in case you haven't noticed, we like to argue, er, debate on this board, pertinent or not.

BTW, I don't remember if tht was a Cycle World or "Cycle" magazine I read that article about the RD400 in, but I have it in a paperback book somewhere stashed away. Years ago, before the net, I read a lot of zines. Now days, not so much.

 

[leekellerking]

Yeah, I know, but in case you haven't noticed, we like to argue, er, debate on this board, pertinent or not.

I dispute that!

 

[Johnny Monsoon]

We were talkin' MXers, right? Chris S was, anyway. If you wanna WIN, you won't be on a KLR. I'll be takin' the checkers ...

Not if it is an endurance race. In which case a big thumper will probably be along to pull you behind it to the repair shop.

Debate started when 2 strokes were noted as not being on Honda's list.

It is a superior design for racing.

So far as I know, all the most historic and prolific engines in any class of racing have been 4 stroke. SAAB had some success with their early 2 stroke WRC cars in the 60s, but even they were second fiddle to 4 strokes very early in the game, and no one ever went back. F1 is not a 2 stroke. NASCAR doesn't use 2 stroke (or any of the sub-BORING... errr... NASCAR subracing brackets).

MX is the only place where 2 strokes have dominated; and the reason they do is that they are considered expendable engines that can be run to extreme tolerances with very little regard to longevity at the expense of shaving a couple of pounds, and even the weight is so minimal it is absurd to mention anymore: Just a couple of years ago, I believe it was Honda, that had one of their 4 stroke engines within 4 pounds of a 2 stroke, and it won accolades for providing amazing low torque which allowed more throttle control and a cooler clutch, which locked up better, which let the bike make it around the track just as fast as it's 2 stroke cousin despite lower revving. The whole "4 strokes are soooo much heavier than 2 strokes" is very akin to "Don't use that front brake, it'll kill ya!" or "Wearing a helmet will KILL you", or "Loud pipes save lives!"

 

[Johnny Monsoon]

I suspect he's never been on a MX track. I'd worry about being run over or landed on riding a KLR for MX! I'm beginning to wonder if he's ever even heard a modern MX bike, since I couldn't barely hear my old YZ250 or current 300 XC-W over the average CRZ/RMZ/KXF/YZF.

IZ ME (darn wifey could only get one angle 'cuz she was skeert; is the small jump)...

Whatcha don't see is the two smokers behind me that I just blew away from. They'd match me on the tight corners, but not the more open areas; they couldn't even come close. But, that's what my XRR was designed for. If I wanted a tight woods bike it'd be a 400ish cc 4 stroke.

I love how folks tell you what you know when you disagree with them and you have experience...

Lessee... while not a pro MX racer, have done MX, is fun. Never needed a two stroker to get around another two stroker though. Weird!

Also, between the two of us, probably the only one who was hired out of high-school auto shop to maintain two fleets of construction equipment (and the bosses bikes) for five years...

But... you're right, you know more than me, 'cuz you said so, and since you did it on the interwebz, it must be trooz!

 

[Johnny Monsoon]

Yeah, I know, but in case you haven't noticed, we like to argue, er, debate on this board, pertinent or not.

For as much as we might disagree on this topic, I have no ill will whatsoever; in fact, this would be a lot more fun with a beer between us!

 

[Jack Giesecke]

Not if it is an endurance race. In which case a big thumper will probably be along to pull you behind it to the repair shop.

I remember finishing 2nd in class on an RD400 in a 6 hour WERA national once. It was just a quick toss together team, me and Bill Syphan. Pill was on the bike on the last lap and blew out the rear PZ2 Michelin on the banking, nearly kissed the wall, but came across to take the checkers. That tire was new at the start, not even scrubbed in before practice. We wore the tire out, but in 3 years of racing, I never wore out a top end. I only put rings in it between the second and third seasons just because. I don't think they really needed it. Lots of four strokes DNFed that day, though. I crashed out of the grand national final at TWS in '78 while running up in the top three novices. Seems a four stroke (thanks, Beneker) dumped oil on 8A in the fast line and the sorball got me. That's what four strokes are good for, oiling the track down. Interestingly, that spot also got Freddy Spencer and Skip Aksland on their TZ750s. They were more than a little hot about Benekers POJ street bike.

So far as I know, all the most historic and prolific engines in any class of racing have been 4 stroke. SAAB had some success with their early 2 stroke WRC cars in the 60s, but even they were second fiddle to 4 strokes very early in the game, and no one ever went back. F1 is not a 2 stroke. NASCAR doesn't use 2 stroke (or any of the sub-BORING... errr... NASCAR subracing brackets).

Apples and oranges. Who cares about NASCRAP? Not me. We're talkin' MOTORCYCLES here. Yeah, back in the 50s, before the expansion chamber and the reed valve and yadda, yadda, yadda, big 500cc single cylinder OHV thumpers ruled. So what?

MX is the only place where 2 strokes have dominated; and the reason they do is that they are considered expendable engines that can be run to extreme tolerances with very little regard to longevity at the expense of shaving a couple of pounds, and even the weight is so minimal it is absurd to mention anymore: Just a couple of years ago, I believe it was Honda, that had one of their 4 stroke engines within 4 pounds of a 2 stroke, and it won accolades for providing amazing low torque which allowed more throttle control and a cooler clutch, which locked up better, which let the bike make it around the track just as fast as it's 2 stroke cousin despite lower revving. The whole "4 strokes are soooo much heavier than 2 strokes" is very akin to "Don't use that front brake, it'll kill ya!" or "Wearing a helmet will KILL you", or "Loud pipes save lives!"

There's this little series over in Europe called FIM. They used to run what they called 500cc GP. From the mid 60s until very recently, the 500cc two stroke DOMINATED. Roberts (both Sr and Jr), Spencer, Lawson, Schwantz, Rainey, just some of the names you may have read about who won world championships on two strokes. Honda HRC TRIED (they're very pro four stroke, like you) to build and make an oval piston 32 valve GP machine work in the 80s, worthless waste of money, two strokes just RULED.

So, faced ith wanting to phaze out the two stroke a few years ago, FIM created "motoGP". They allowed 990cc four strokes against the 500cc two strokes (sound familiar?). The two stroke privateer guys ran pretty well, but couldn't fight the added displacement. Finally, the two strokes were just out right eliminated by the rules. The 250 and 125 classes are still all two stroke. No one dare run a 125cc four stroke against a 60 horsepower factory 125cc Aprilia 2 stroke, woulen't stand a chance. But, be heartened as there have been roomers that the 2 strokes will be eliminated in the smaller classes, too. They'll be way boring for a while, I'm betting, as there's not near the development money in the smaller classes and the attention of the big factoryies is elsewhere. The smaller factories have always been attracted to the smaller classes first due to the lower costs of designing and building competitive engines, which will go way up with four strokes. For instance, when Suzuki broke in to GPs in the 60s, they first won the 50cc world championship. It was done with a two stroke. In 125s, the Yamaha twins outran the 5 cylinder four stroke Hondas. Yamaha put Honda to rest with two strokes and Honda just up and quit GPs through the 70s, came back in the 80s with their own two strokes.

Yeah, okay, MX is the only place..... I even saw in one of the gas classes where an H2 Kawasaki was dominating in drag racing against MODERN machines in the class. I don't follow drag racing, but thought that was interesting.

There was even a two stroke TZ750 based flat tracker that team Yamaha put togethr in 1975 to try to help KR in his quest to retain the number one plate as his XS650 based tracker was uncompetitive and kept breaking. Only the King could ride that thing 120 horsepower at the rear wheel DETUNED to try to make it more tractable. Here's the story.

http://www.superbikeplanet.com/dontpaymeenuff.htm

The race on youtube

http://www.youtube.com/watch?v=nj97mObeEyw

Oh, la-de-dah, isn't life grand at the front of the pack Jay? Yes, dear Corky, dreadful about our chum Roberts having such a bear of a time on that contraption ... say, what's that frightful noise?

A quote after that race from Corky Keener who was leading to the last lap. "I heard that screamin' son-of-a-***** coming and I knew it was over."

A vid of KR preparing for a parade lap on his famous TZ flat tracker. GOD, what an evil motorcycle!

http://www.youtube.com/watch?v=IEQAnCL3e5Q

 

[Johnny Monsoon]

You and I both know that it has been several years now, and that all the pro riders agree, hands down, that the 4 stroke engines dominate and are more, everywhere, than the 2 smokers were.

Faster, and Faster & Faster...

And, you can't really compare displacement. It's much more equitable to say a 500cc 2 stroke is equal to a 1000 4 stroke due to combustion strokes per engine. And the weight difference between those two engines is marginal. The 2 stroke has to be built beefier to not grenade, and will run hotter which will kill the oil in a hurry. A 4 stroke is much more 'climate controlled' and maintains its tolerances much better, thus giving much more consistent power. That, largely, is why a 4 stroke is more reliable, and why the engines are similar weights.

This really would be better 'at the bar' banter though... When ya gettin' your backside up here to do some yakkin', drinkin', and otherwise engaging in general mischief?

 

[Jack Giesecke]

You and I both know that it has been several years now, and that all the pro riders agree, hands down, that the 4 stroke engines dominate and are more, everywhere, than the 2 smokers were.

Faster, and Faster & Faster...

And, you can't really compare displacement. It's much more equitable to say a 500cc 2 stroke is equal to a 1000 4 stroke due to combustion strokes per engine. And the weight difference between those two engines is marginal. The 2 stroke has to be built beefier to not grenade, and will run hotter which will kill the oil in a hurry. A 4 stroke is much more 'climate controlled' and maintains its tolerances much better, thus giving much more consistent power. That, largely, is why a 4 stroke is more reliable, and why the engines are similar weights.

This really would be better 'at the bar' banter though... When ya gettin' your backside up here to do some yakkin', drinkin', and otherwise engaging in general mischief?

OF COURSE a 990cc four stroke has more than a 500 cc two stroke!

And, yes you CAN compare cc for cc. In 1975, when I started road racing with CRRC, 410 production class, was 410 production class. The fact that 350cc two strokes ruled it, well, buy a two stroke if you wanna win. Honda figured that out in the 80s, can't beat 'em, join 'em. It is still the rule in 125 and 250, however temporary, straight up, 125 against 125, 250 against 250, not 125 against 250 or 250 against 500....yet. Face it, the two stroke is the superior design for racing motorcycles. There is no way around this unless, maybe, like in autos, you toss in turbocharging. That would even things up a bit.

The ONLY way four strokes can compete is with rules allowing more displacement. That's just fact. Now days, they even allow traction control, which would take the bite out of the two stroke power band if it had been allowed then.

If you will read some of the history which I lived, you will note that in the 60s, the two stroke got advanced enough in design by the Japanese to totally dominate the once all powerful four strokes. It took advancements like DKW's (IIRC) expansion chamber exhausts and schnerl scavenging, first advanced in the 30s to replace loop scavenging and necessary for ligher pistons and higher RPMs, to bring the first piston port two strokes to equality with the four strokes. Understanding of the fluid dynamics of induction, the development of rotary and case reed induction and improvements in reed materials, the development of the variable tuned exhaust port (power valves) all came along and helped get 2 strokes superior two 4 strokes for output and kept them way ahead. Newer advancements like traction control (which I don't really like) could be applied to them to really help off corner control.

Face it, you don't like two strokes, fine, but they are superior designs for racing. You cannot intelligently argue otherwise. Facts is facts. Now, thanks to Algore, they're on the way out, but only by manipulation of the racing rules, not for any inferiority on the track.

BTW, running hotter "kills the oil" in a two stroke? That right there is a good one. WHAT oil? The oil lubes the engine and then gets discarded as in burned up. Let's see, my 125 ran 60-70 degrees C optimally. I don't think that's any hotter than a four stroke anyway. See, I've actually OWNED the motorcycles of which I speak and have raced them, sometimes successfully despite my somewhat limited natural talent on the track. The bikes I have always been most successful on have been two strokes. That might have something to do with my quite limited budget or the fact that I just prefer them, true racers, no pretense of street, no headlight, no horn. GP stuff is MADE to go fast, only to go fast. Recent years, I really couldn't afford all the A kit stuff and stuff I'd need to keep up with the fast kids and being 200 lbs didn't help on a 160 lb motorcycle.....but I found that small tracks and minis evened the playing field somewhat and I learned to ride harder, push harder, on the little KX. I never was THAT good on a GP cause I just never pushed 'em hard enough. Funny, but I got my fastest on little tracks like katy where I could slide both ends, back it in, get squirrely and get away with it. If I did crash, it didn't hurt as bad or cost me as much, more important to me than hurt until I lost my medical insurance. BUT, Ill always love the little GP stuff over any 4 stroke ever. They suit my late braking, rear tire off the ground and sideways style I like to use to pass and just plain RAIL when you keep 'em on the fast line and maximize corner speed. I've never quite gotten that comfortable on my XR100 tards due to the excessive compression braking. I ride my two stroke a lot harder and faster, probably always will. I had a HUGE good time on John Casley's NSR when we ran it in TMGP and CMRA mini enruance for WRW racing, too. I could rail on that thing on a good day. I could get it down in the 36s at KATY before the track expansion which is only 2 seconds slower than my KX. The thing only makes about 8 horsepower in stock 50cc trim. I was actually faster on it there as a 50 than as a 63! It was easier to ride on the kart tracks. Cheap thrills compared to four strokes in minis. If you have that much of a bias that you won't get on what wins, well, you'll lose. That's the way racing is. It's not a matter of what you like, only in Vintage where winning isn't everything do people ride losing motorcycles and enjoy it.

 

[Jack Giesecke]

One question on the equity thing. If you can allow 1000cc four strokes against 500cc two strokes and call it fair, what about desmo valves? The Ducatis are kickin' butt power wise with desmo valves in both superbike and GPs. Is it fair? Should they be allowed lower displacement because of superior engine design? Just askin'.

 

[Johnny Monsoon]

OF COURSE a 990cc four stroke has more than a 500 cc two stroke!

And, yes you CAN compare cc for cc. In 1975, when I started road racing with CRRC, 410 production class, was 410 production class. The fact that 350cc two strokes ruled it, well, buy a two stroke if you wanna win. Honda figured that out in the 80s, can't beat 'em, join 'em. It is still the rule in 125 and 250, however temporary, straight up, 125 against 125, 250 against 250, not 125 against 250 or 250 against 500....yet. Face it, the two stroke is the superior design for racing motorcycles. There is no way around this unless, maybe, like in autos, you toss in turbocharging. That would even things up a bit.

The ONLY way four strokes can compete is with rules allowing more displacement. That's just fact. Now days, they even allow traction control, which would take the bite out of the two stroke power band if it had been allowed then.

If you will read some of the history which I lived, you will note that in the 60s, the two stroke got advanced enough in design by the Japanese to totally dominate the once all powerful four strokes. It took advancements like DKW's (IIRC) expansion chamber exhausts and schnerl scavenging, first advanced in the 30s to replace loop scavenging and necessary for ligher pistons and higher RPMs, to bring the first piston port two strokes to equality with the four strokes. Understanding of the fluid dynamics of induction, the development of rotary and case reed induction and improvements in reed materials, the development of the variable tuned exhaust port (power valves) all came along and helped get 2 strokes superior two 4 strokes for output and kept them way ahead. Newer advancements like traction control (which I don't really like) could be applied to them to really help off corner control.

Face it, you don't like two strokes, fine, but they are superior designs for racing. You cannot intelligently argue otherwise. Facts is facts. Now, thanks to Algore, they're on the way out, but only by manipulation of the racing rules, not for any inferiority on the track.

BTW, running hotter "kills the oil" in a two stroke? That right there is a good one. WHAT oil? The oil lubes the engine and then gets discarded as in burned up. Let's see, my 125 ran 60-70 degrees C optimally. I don't think that's any hotter than a four stroke anyway. See, I've actually OWNED the motorcycles of which I speak and have raced them, sometimes successfully despite my somewhat limited natural talent on the track. The bikes I have always been most successful on have been two strokes. That might have something to do with my quite limited budget or the fact that I just prefer them, true racers, no pretense of street, no headlight, no horn. GP stuff is MADE to go fast, only to go fast. Recent years, I really couldn't afford all the A kit stuff and stuff I'd need to keep up with the fast kids and being 200 lbs didn't help on a 160 lb motorcycle.....but I found that small tracks and minis evened the playing field somewhat and I learned to ride harder, push harder, on the little KX. I never was THAT good on a GP cause I just never pushed 'em hard enough. Funny, but I got my fastest on little tracks like katy where I could slide both ends, back it in, get squirrely and get away with it. If I did crash, it didn't hurt as bad or cost me as much, more important to me than hurt until I lost my medical insurance. BUT, Ill always love the little GP stuff over any 4 stroke ever. They suit my late braking, rear tire off the ground and sideways style I like to use to pass and just plain RAIL when you keep 'em on the fast line and maximize corner speed. I've never quite gotten that comfortable on my XR100 tards due to the excessive compression braking. I ride my two stroke a lot harder and faster, probably always will. I had a HUGE good time on John Casley's NSR when we ran it in TMGP and CMRA mini enruance for WRW racing, too. I could rail on that thing on a good day. I could get it down in the 36s at KATY before the track expansion which is only 2 seconds slower than my KX. The thing only makes about 8 horsepower in stock 50cc trim. I was actually faster on it there as a 50 than as a 63! It was easier to ride on the kart tracks. Cheap thrills compared to four strokes in minis. If you have that much of a bias that you won't get on what wins, well, you'll lose. That's the way racing is. It's not a matter of what you like, only in Vintage where winning isn't everything do people ride losing motorcycles and enjoy it.

Displacement is an erroneous measurement comparing the engines. You can't do it. Sure, a 500cc two stroke can do what a 1000cc 4 stroke can, but it works twice as hard to do it; and to get that 'double power per liter' that a two stroke offers, it has to equal twice the volume of a 4 stroke's single compression stroke per cylinder. That's just the facts. In which case, you actually get the same power for less than half of the displacement PER COMPRESSION STROKE than you do with a 2 stroke, which is why 2 strokes get worse mileage. A two stroke has to do twice the work in half the time to equal the same distance.

Also, ummm... MotoGP is 4 stroke evolved from 2 stroke. So, ummmm, clearly the best engine for motorcycle racing is a 4 stroke; especially since that's the pinnacle of evolution of the high performance motorcycle engine (and, weird, they're reliable too!). AND, while they reduced engine size 110cc (to 800cc) they are getting faster bikes and lap times... Faster than their two stroke predecessors ever were.

 

[Jack Giesecke]

Displacement is an erroneous measurement comparing the engines. You can't do it. Sure, a 500cc two stroke can do what a 1000cc 4 stroke can, but it works twice as hard to do it; and to get that 'double power per liter' that a two stroke offers, it has to equal twice the volume of a 4 stroke's single compression stroke per cylinder. That's just the facts. In which case, you actually get the same power for less than half of the displacement PER COMPRESSION STROKE than you do with a 2 stroke, which is why 2 strokes get worse mileage. A two stroke has to do twice the work in half the time to equal the same distance.

Also, ummm... MotoGP is 4 stroke evolved from 2 stroke. So, ummmm, clearly the best engine for motorcycle racing is a 4 stroke; especially since that's the pinnacle of evolution of the high performance motorcycle engine (and, weird, they're reliable too!).

Sure you can do it. All it takes is a bore gauge and a caliper. pi times 1/2D squared x stroke times number of cylinders. Simple geometry. It works. TZ250s were 54mm x 54mm times two cylinders. Do the math and see for yourself. Two strokes took over on an equal ground in the 60s. In the late 90s, the ecofreak tree huggers took over politics and the superior design which happened to not be able to pass emissions tests (like racing is a real harm to the environment ) were ruled out of racing. They did not get passed by superior technology. They had to be ruled ineligible. It's happened to lawn mowers, too. I loved the old Lawn Boys, quiet, last forever, a little expensive, but worth the price. Next, likely, is trimmers and chain saws and leaf blowers and such. Ever pick up a four stroke Troy Bilt trimmer? Light for a four stroke, but a pain in the arm compared to the two stroke. But, wouldn't wanna pollute with that weed whacker, would we?

Have you ever even OWNED a two stroke? If so, what was it, an Islo? Some two strokes were MORE reliable than a LOT of four strokes in the 70s. The AMF Harley for instance, the TZs would outlast. Suzukis two strokes were the equal of anything, require less money per mile to maintain that any four stroke at the time. I've seen a few Z1s that clocked 80K or so on rings. Wings, of course, could go 150K, but they were basically Subaru engines with two wheels. Better built that the Subarus of the time, though, LOL. As I said, I had a GS750 air cooled 8 valve four stroke that WASTED its rings in 22,500 miles. My RDs were good for at least 30K or more and the top end was a LOT easier to do. Water buffalos could run 100K in stock tune, water cooling really helps regardless of strokes, but especially the two stroke.

 

[Johnny Monsoon]

Sure you can do it. All it takes is a bore gauge and a caliper. pi times 1/2D squared x stroke times number of cylinders. Simple geometry. It works. TZ250s were 54mm x 54mm times two cylinders. Do the math and see for yourself. Two strokes took over on an equal ground in the 60s. In the late 90s, the ecofreak tree huggers took over politics and the superior design which happened to not be able to pass emissions tests (like racing is a real harm to the environment ) were ruled out of racing. They did not get passed by superior technology. They had to be ruled ineligible. It's happened to lawn mowers, too. I loved the old Lawn Boys, quiet, last forever, a little expensive, but worth the price. Next, likely, is trimmers and chain saws and leaf blowers and such. Ever pick up a four stroke Troy Bilt trimmer? Light for a four stroke, but a pain in the arm compared to the two stroke. But, wouldn't wanna pollute with that weed whacker, would we?

Have you ever even OWNED a two stroke? If so, what was it, an Islo? Some two strokes were MORE reliable than a LOT of four strokes in the 70s. The AMF Harley for instance, the TZs would outlast. Suzukis two strokes were the equal of anything, require less money per mile to maintain that any four stroke at the time. I've seen a few Z1s that clocked 80K or so on rings. Wings, of course, could go 150K, but they were basically Subaru engines with two wheels. Better built that the Subarus of the time, though, LOL. As I said, I had a GS750 air cooled 8 valve four stroke that WASTED its rings in 22,500 miles. My RDs were good for at least 30K or more and the top end was a LOT easier to do. Water buffalos could run 100K in stock tune, water cooling really helps regardless of strokes, but especially the two stroke.

You're giving a volume measurement, but that isn't duty cycle. Duty cycle of a 2 stroke is twice what a 4 stroke engine is. Thus, displacement is only half the equation for power. Displacement per stroke would be accurate, which makes the two engine configurations nearly equal, and actually giving a slight edge to the 4 stroke. So, either double the displacement of a 2 stroke, or reduce the power by half. Either way, that gives you a power per liter ratio that is accurate.

Yes, as I've said (if you've been reading) I was a light engine mechanic, and most of those were two strokes.

There's no way any mechanic, and very, very few owners (I'd probably have better odds playing lotto) tell me that a 2 stroke will outlive a 4 stroke engine. Oh, and it 'aint been the '70s for a goodly while now. Maybe that's the issue!

 

[Rman of 237]

Hands down, this is the best thread I've read in a long time!! Jack G needs to write a book. Seriously, write it down!! This is amazing!!
Look, I ride and have ridden 2 and 4 strokes, mostly dirt related but the only true street bike I've ever owned is an RZ350. I bought it new in '84 in Waco(Steakley Bros. Yamaha) and remember waxing all the "Baylor Boy's" s on their daddy's loners on Valley Mills on Sat. nights bone stock.
I'm very happy with my current line up but the bike I appreciate owning most is the RZ. Maybe you've read the story on other forums but it was trashed by a cow getting into the barn and stomping it up pretty good. It's now running like new but with a lot of cosmetic work still to go.
Now to you 2T naysayers, if you've never ridden an RD or RZ, what's your point? Get on one and ride it!! I dare ya'!!!

 

[Johnny Monsoon]

Hands down, this is the best thread I've read in a long time!! Jack G needs to write a book. Seriously, write it down!! This is amazing!!
Look, I ride and have ridden 2 and 4 strokes, mostly dirt related but the only true street bike I've ever owned is an RZ350. I bought it new in '84 in Waco(Steakley Bros. Yamaha) and remember waxing all the "Baylor Boy's" s on their daddy's loners on Valley Mills on Sat. nights bone stock.
I'm very happy with my current line up but the bike I appreciate owning most is the RZ. Maybe you've read the story on other forums but it was trashed by a cow getting into the barn and stomping it up pretty good. It's now running like new but with a lot of cosmetic work still to go.
Now to you 2T naysayers, if you've never ridden an RD or RZ, what's your point? Get on one and ride it!! I dare ya'!!!

They still sell 'em in Japan; the street-able Ninja 250cc 2 strokes. Had one for a while. Probably perfectly suited to that environment and those roadways, but man, that thing was screaming all the time, and I smelled just like the exhaust after even the shortest rides. My little Ninja 400 was a better bike all around though. Not as punchy, but required a lot less attention.

 

[Jack Giesecke]

Probably perfectly suited to that environment and those roadways, but man, that thing was screaming all the time, and I smelled just like the exhaust after even the shortest rides

Sounds divine. Just run some bean oil in it, intoxicating. As they say, "Smells like....VICTORY!" Used to love to burn up my left over race gas in the lawn mower. I could visualize TWS turn one as I made the laps of my back yard.

 

[Johnny Monsoon]

Sounds divine. Just run some bean oil in it, intoxicating. As they say, "Smells like....VICTORY!" Used to love to burn up my left over race gas in the lawn mower. I could visualize TWS turn one as I made the laps of my back yard.

Victory smells like JP8 these days...

Racing Mowers! Man, just look at that crowd; nuthin' draws 'em in like a good mower race!

Aren't those four strokes too?