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1000cc 2-stroke...

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Jack Giesecke said:
You just keep it on the pipe, don't let it fall off. Throttle control is a lot more predictable that way. Slam the down shifts and over rev it into corners, no valves to float, ya know. Come off the corner on the pipe. That's the trick. But, then, when you got over 100 hp at the right wrist, it's still intimidating, I reckon. It's a far cry from a 125, put it that way. :lol2: I never got to ride more'n a 250 two stroke except for street RDs which don't count.

I know when David Green (a friend from the past who's no longer with us) won the Daytona 250 novice pro race in 81, he was given expert status in 82 and eligible for F1. He had no problem with money, dad ran "Durwood Green construction" in the Houston area and David got any toy he wanted, paid cash for a Ferrari 308, that kind of rich. :lol2: So, for 82, he bought a TZ750 and an ex-euro RG500 Suzuki production racer. When he got 'em to TWS at a "test day" (we didn't have track days back then) both those bikes scared him so bad, he sold 'em and bought a new TZ250 for the season. :rofl: I never got to ride one, but I think I'd been like David, would have scared me to tears, cry like a girl. :rofl:

Actually, Eric, you were a far faster rider than David was. How David won that Daytona race, I'll never know. I could run with the guy at Oak Hill and I had half the motorcycles he had. I think he realized he didn't have any business on a 750 and that it would hurt him. I'm sorta glad I never got a chance to try one. :rofl: I think that day at Daytona, David must have pulled something out I never saw in him before or since, but he beat a guy named Donny Green that day, fast rider out of California, and a 16 year old fast kid that went on to set 250 class records in AMA, Rich Oliver. That race was David's 15 minutes of fame.:lol2:

So, we can all sit here and awe at what we might do with a motor like that, but I don't know about myself. I might be more than a little intimidated by that much power in a 2 stroke. :lol2: A man's got to know his limitations.
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These things are very fun when somewhat modernized:
 

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The stock CR500 scares me, so I think I'll pass. :nono:

So, John, when you kill yourself on that thing, can I have your SD-R? :trust:
 
1TallTXn said:
The stock CR500 scares me, so I think I'll pass. :nono:

So, John, when you kill yourself on that thing, can I have your SD-R? :trust:
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Leave the tuned pipes off of a two stroke and you will be amazed at how broad the power band becomes. I once rode my H1 with only the header pipes on it, no mufflers, and the engine pulled much harder at the low rpms without that big hit in power at 6000 rpm.

The last thing you want on an observed trials bike is an engine that has an on off switch for a throttle, guess what type of engine is on most trials bikes.
 
Ben Eberle said:
Leave the tuned pipes off of a two stroke and you will be amazed at how broad the power band becomes. I once rode my H1 with only the header pipes on it, no mufflers, and the engine pulled much harder at the low rpms without that big hit in power at 6000 rpm.

The last thing you want on an observed trials bike is an engine that has an on off switch for a throttle, guess what type of engine is on most trials bikes.
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It's not just the pipe tuning, but also port tuning and intake tract tuning that dictates the power band of any two stroke. It's all about port time/area. For a grasp of the fluid dynamics of it all, read "Two Stroke Tuner's Handbook" by the late Gordon Jennings. Far too complicated for a post on a BBS. Now days, there are computer engine flow modeling programs that will do the math for you. You must measure port areas and timing and make the inputs, but it will draw power curves for you, including pipe tuning and intake tract tuning. Buddy of mine has such a program and it's pretty danged impressive. He built my KX motor using it. I sorta wish we'd left it stock, though. We built it for the big tracks of CMRA and I wound up using it mostly on TMGP kart tracks over the years. Friggin' peaky with those radical ports on such tight tracks. You really have to have the gearing right and keep it up on the pipe everywhere, but do that and it flies. :mrgreen: It is a big handful in traffic, though. It's a lot of fun. It'll get little power wheelies and will actually power slide the rear out of corners on kart tracks, like a motoGP scaled WAAAAAAY down. LOL!
 
Jack Giesecke said:
It's not just the pipe tuning, but also port tuning and intake tract tuning that dictates the power band of any two stroke. It's all about port time/area. For a grasp of the fluid dynamics of it all, read "Two Stroke Tuner's Handbook" by the late Gordon Jennings. Far too complicated for a post on a BBS. Now days, there are computer engine flow modeling programs that will do the math for you. You must measure port areas and timing and make the inputs, but it will draw power curves for you, including pipe tuning and intake tract tuning. Buddy of mine has such a program and it's pretty danged impressive. He built my KX motor using it. I sorta wish we'd left it stock, though. We built it for the big tracks of CMRA and I wound up using it mostly on TMGP kart tracks over the years. Friggin' peaky with those radical ports on such tight tracks. You really have to have the gearing right and keep it up on the pipe everywhere, but do that and it flies. :mrgreen: It is a big handful in traffic, though. It's a lot of fun. It'll get little power wheelies and will actually power slide the rear out of corners on kart tracks, like a motoGP scaled WAAAAAAY down. LOL!
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Yes, the porting has to agree with the tuned pipe's rpm. But take the tuned pipe (expansion chamber) off and run the exhaust straight out of the port like a chain saw and the engine makes much less power, however, it will be equally unpowerful at all rpms. The big hit when the engine comes on the pipe will be gone.

Two strokes can be quite torquey if they are designed that way, ever ride an old Jawa 350 or a Suzuki GT 750?

Most people would probably go faster with a more mildly tuned engine on the average race track. A mildly tuned engine helps you be fast on the slowest part of the race course where you spend the most time. To understand the concept, consider riding two miles going 10 mph for the first mile and 30 mph for the second mile. Your average speed is not 20 mph but only 15 mph.
If your goal is to average 20 mph on that two mile run, you could either go 10 mph for the first mile and ride the second mile at the speed of light, or you could increase the speed of the first mile to 15 mph and finish the second mile at 30 mph.
 
Ben Eberle said:
Yes, the porting has to agree with the tuned pipe's rpm. But take the tuned pipe (expansion chamber) off and run the exhaust straight out of the port like a chain saw and the engine makes much less power, however, it will be equally unpowerful at all rpms. The big hit when the engine comes on the pipe will be gone.

Two strokes can be quite torquey if they are designed that way, ever ride an old Jawa 350 or a Suzuki GT 750?

Most people would probably go faster with a more mildly tuned engine on the average race track. A mildly tuned engine helps you be fast on the slowest part of the race course where you spend the most time. To understand the concept, consider riding two miles going 10 mph for the first mile and 30 mph for the second mile. Your average speed is not 20 mph but only 15 mph.
If your goal is to average 20 mph on that two mile run, you could either go 10 mph for the first mile and ride the second mile at the speed of light, or you could increase the speed of the first mile to 15 mph and finish the second mile at 30 mph.
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I owned a couple of GT550s and a BUNCH of Yamaha RDs. The RDs would kick the GT's butts 9 ways to Sunday even with stock exhaust on both. :rofl: The ports in those GTs were tiny. They pulled like a tractor from 3K up. They were not lug friendly, though. Lug the motor too much and it'd foul plugs left and right. They had the crankcase/cylinder direct injection, which in theory oils the bearings more direct, but in actual practice didn't mix the oil well before entering the transfer ports. Thing would smoke like a mosquito sprayer when you got on it from low RPM. Sorta like James Bond's Astin Martin's smoke screen machine. :rofl:

You can tune an expansion chamber for low end, to, ya know. Long tapered cones and pipe and small pipe diameter. The shallow angle tapers on the cones make for a wider power band. A longer pipe makes it peak at lower RPMs (longer resonance time in the pipe). It's all in the shape where expansion chambers are concerned, all about pressure wave timing back to the exhaust port.

Another reference to tuning my 80, but I had a FMF rev pipe, short and fat for high rpm, on the bike when Duncan cut the ports. Rather than shorten the pipe to match the porting, we wrapped the first half of the pipe, the divergent cone, with insulation tape. What that does is increase exhaust gas temperature. It's an old tuning trick, just runs the gas hotter which increases the speed of the pressure waves in the pipe which causes it to work at a higher RPM, like cutting the pipe down, but easier to change if it ain't right. :mrgreen: I wrapped the thing full length at first, it pulled 13, 750 rpm (inductive tach I put on it) and blew my crank. :rofl: With just the head and divergent cone wrapped, it pulled just under 13,000 rpm, about 12,500 is peak. It comes on the pipe about 11,000 now, a thousand rpm higher than it did without the tape. AND, the crank survives even the big tracks. On the little tracks, it's in the throttle a lot less and the crank seems to last forever. :mrgreen: It's a tough little fart to ride, but it rewards you for your efforts when you get it right. The goal here is to win races and light speed is all that's acceptable. :mrgreen:

One of the things I always liked about two strokes is that, if you understood 'em, you could make 'em REALLY hot without a lot of hardware. No cams or valve springs or titanium valves or other such worthless stuff. Just put a set of good pipes on it and you can increase an RD Yamaha's peak output by 30 percent and make it a lot more fun, in a hooligan sort of way, to ride. Pipes on modern 4 strokes are more about noise than performance. Most, you can't even tell the difference. On an RD, when you stuck Bassani pipes on it, it hit 5500 rpm in second and painted the sky with the headlight, you KNEW you had a lot more punch. :rofl: Of course the down side is if you didn't jet it and spent too much time WFO, you could stick it, but hey, you have to learn somehow, right? And, I mean, that's what they sell muratic acid for.
 
I had a '75 model Suzuki water buffalo. It was the year model they changed the porting to make them sportier. It was a little more peaky than the earlier models and had a slightly higher hp rating. It ran okay but nothing like my '75 Z1. I luuved the way it sounded though. It wasn't very good on the highway between 55 - 65 mph though as I could never tune out the light load surging. Once up to 70 mph and above it ran very smooth. Used a good bit of fuel though, about 35 mpg was the best it would do. Sold it to a guy who got hit by some woman in the parking lot of the Galleria in Houston soon after he bought it. He was OK but the bike was a goner. So sad.

Kevin
 
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