Can someone tell me what is causing the Raptor motor to fall a little short on peak HP for a 650 class engine? Does the lighter crank have something to do with it? Cam timing? Has Yamaha traded off a few peak HP for more of a 2-stroke hit?

 

ScoobyDFW.....

IF (it's a big *if*) the 660r Raptor motor is, as you say "down on horsepower" you can bet it was done in an effort to de-tune the thing for use in a heavier Quad. As you know, the motor was originally a 2-wheel motorcycle engine, and has been adapted for use in the Raptor. The goofy 1st.
and 2nd. gear ratios sure look to me like an attempt to calm down a wheelie monster. The seemingly "built-in" restrictions in both the intake and exhaust tracts are another indicator.

You can go out to MuZ's Web-site and I think you will find there a listing of the final drive ratio for their 660 motorcycle. By actual test, on the high banked Daytona Track, it got up to 118 MPH in high gear. It's pretty easy from there to compute
max rpms given the height of the stock rear tire.

It does seem like the Raptor dyno figures are a very large mystery...Yamaha should have released the figures right away.

Flyin' Ryan

 

Yamaha france claims 55HP, must be at the crank though.

 

Yes, I believe that Yamaha detuned the Raptor. But, as it is with any other atv, the tuning will arrive soon, as will the many mods for the 660R. If I had one, the first thing I would do is change the gearing on it. Just my opinion.

Kyle

 

Scott at Curtis Sparks emailed me back the Full exhaust (NOT a SLIP ON) is rippin, it will be ready for sale at the end of the month, The first 2 production runs are sold out so order now if you want one, they are also selling about 5 of the ignition advance keys per day and he said 5-6 more weeks and the full National Kit will be ready to roll.