Yz250f

yzeater

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May 21, 2001
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#1
How can a 250F rev to 13500 rpms? How many rpms can a 80 two stroke, a 500 two stroke, a 50 four stroke and a 650 four stroke rev to? I know it's a lot, but if we work together, we can get it done.:D
 
Joined
Feb 12, 2001
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#2
13.5K is the result of a short stroke + light piston, pin, and rod + low valvetrain mass + small crank angle + proper intake and exhaust flow geometry. oh, a dry sump helps too, no oil windage.

what you should be asking is how a multicylinder 1000bhp formula 1 race car engine can rev to 20K rpm.

the wrooster
 
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Jun 15, 2001
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#3
Well 4 cyl streeet bikes have been hitting 13 K for some time now. The 5 valve design has been on the Yamaha street bikes since the Genisis FZR bikes I think. This teck has been around for some time, it is just now trickeling down to the dirtbike market. What surprises me the most is why direct injection 2 stokes with oiless bearings (no mix, no smoke) like the Bimota 500cc street bike uses has not crossed over to the car and street bike race world. I saw an RZ 350 on the way home from work and remembered how cool they were. 1986 2 cyl 2 stroke street sport bike. After they outlawed em in the states, the 2 cyl 2 stroke found its way in to the Banshee.