Go to ebay there is a 500cc trx250r on there. It says it will do 85mph in 5th gear. won't even get to 6th gear its so fast!

 

i thought 500's were 5 speeds to begin with

 

I put an 85 CR500 motor in my 85 ATC250R about a year ago. I ended going back to the 250R motor and getting a big bore kit for it. I wasn't all that impressed with the 500. The vibration was thee but it didn't bother me too much. The big time problem was the rear kick starter. I seen the article on the $20000 conversion in the magazine. I bought the motor that came out of a wrecked 250R. So I got the motor, wiring harness, coil, CDI, exhaust, and motor mounts for $500. Off the bottom it absolutely ripped, the mid was about the same as my big bore kit makes but the kit flat blows it away in top end. The 500 was stock except for Boyesen reeds, reed spacer, and porting by JP. It would be good ONLY for dune drags as there are several mods that need to be done to the motor and chasis to keep it ridable. I am much happier with the CT310 big bore kit and I haven't even added a pipe yet. If you are persistent with doing this swap I can tell you what all needs to be done.