I've been doing some reading on this, working on my own ATV. I have a model with the Rotax 1000 engine.

The engine itself probably shouldn't be the only thing upgraded. Consider the clutch. It would need to be either adjusted or upgraded in order to get the power from the engine to the drivetrain. Axles are another part that can be upgraded to thicker, heavier aftermarket parts.

I would start reading stuff from performance vendors. The ones I've mentioned below have been happy to answer every question I've asked.

MrRPM- Big Bore kits, race heads, intakes, cams
Dynojet- Engine tuning modules, Autotune add-ons, LCD displays
SuperATV- Loads of different stuff
CanAmPartsGuy- More good stuff
Demon Axles- Several grades of axles

Good luck with your build!
Mark

 

their is loads of information on this site if you search..

 

Thank you very much, who else knows something, tell me. I'm looking for experts. Tell me more sites where I can buy spare parts

 

Upgrade the clutches, exhaust, intake, and add nitrous, simplest way.

I ran a Gen 1 800 on a 20 shot of nitrous over a year with no issues on a stock motor.

Jeff the bomb, he makes a tuner designed for adding the correct fuel for the setup, and he can put together a full kit for you.