One of the local dealerships had a portable dyno supplying free charts
for anyone who wanted to bring their bikes and atvs. I don't remember
the exact number that Yahama was quoting for HP but I thought it was
about high 40's. My Raptor is stock except slipon pipe, rejet and frt
sprocket. At the rear wheels, the dyno peaked out at 33 HP. The operator
mentioned that typically that there is a 10-12% loss from flywheel to
wheels. That would make the Raptor only about mid to high 30's for HP, a
far cry from the high 40's I thought I read. One more thing, that was in
4th gear, I don't know if more HP comes from different gears, I was
assuming that the computer read the highest reading....
The numbers didn't really matter since I don't race but the interesting
thing was the dyno supplies mph numbers and I was pleased when the
operator did wind the bike out in 5th gear and was clocked at exactly 90
mph... quite a bit more that I expected since I didn't think that a
change in front sprockets would make that much difference. (It was a 2
tooth increase)
Anyway, thought that was interesting....

Mark

 

Welcome to reality. Manufatures and magazines are often quite liberal in their published stats.

 

Two teeth added to your front sprocket probably killed your dyno numbers. It changes everything. You essentially geared it up and lost that grunt. Your quad will show a significant gain in top speed numbers when weight and wind resistance are not a factor. Essentially your dyno test was invalid as to stock HP numbers due to your alteration of the gearing.

 

Could have been a CA model or not jetted properly also. Or, it could be that it only has that much HP.

 

Gearing does not affect HP. If that were the case, everyone would gear for more HP. That would defy the law of conservation of energy.

OTOH - The tall gearing will kill acceleration and decrease torque multiplication at the contact patch of the rear tires as a tradeoff for more space between the gears and a higher top speed (although it won't alter the torque produced by the engine, which is what the dyno measures).

 

I don't know about that jetting. Jetted with slip-on only hitting 33. Doesn't sound right to me you should be in the 38-42 range.

 

Alot off ppl think they make more HP then they really do. I made 38.3HP on my 'shee with just a K&N and toomey silencers with stock pipes. And just because it went to 90MPH on the dyno doesnt mean your quad ill do that. Theres a little thing called wind resistance. [img]i/expressions/face-icon-small-smile.gif[/img] You wont do anywhere near 90mph.


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