I'm going to do a 350x converson with my 250x. I want to get the 393 big bore and the 430 stroker kit from powroll. Will i have to run race fuel or just a 93 octan. How much power and torque would it have and will i be able to keep up with 450rs and 400ex?

 

Fuel depends on the compression ratio. 11:1 piston or lower is fine on 93 octane but much above that compression ratio is going to require race gas. I dont see you having any trouble keep up with 400's in a straight line with this conversion, I dont think that you'll be spanking 450's though with just a big bore and stroker kit. I hope you are planning on doing a good intake and exhaust system.

 

You would be MUCH better off selling the 250X and buying a 400EX or 450R for a number of reasons. The 250X chassis is designed for 250 cc power...not cranked up 350 power. You will have a swell time keeping the front tires on the ground with such a short chassis. And the 250 is narrow, making it tippy at high speeds. You will also loose reverse. And think of the $$ it's going to cost to build up the 350 engine. Then you still have to make some custom mounts or pay someone else to if your not a capable fabricator. I believe you need to spread the frame rails of the 250 to get the 350 in there properly, and maintain a low center of gravity. Then you still will need a custom exhaust which will cost you a fair amount. And make up some sort of an intake. If you sell this creation the resale value will be crap, nobody wants a frankenstein quad. After all the work and $ of the swap you could have easily bought a 400EX and had a better handling quad with better everything and have a much better resale value.


Back in the 90's when there were no 400cc+ four strokes this would have been a hot setup but welcome to 2006