Speed.
Hey Xnatejx,
I think the only way to hit 35mph cheap is to find a 26" bike, Buy a china engine, BREAK IT IN GENTLY, then take it from there.
Mountain bikes are cheap enough, Just go through it entirely to make SURE it's safe,(bearings,brakes,ect.)
I recomend a better engine but with today's economy, as with most of my customers, People are going with what's cheaper.
I've installed a lot of the chinese engines and if treated right, you can get your money's worth out of them.(most of the time.)
Without gearing, a 20 or 24" bike will never hit 40mph. AND I would NEVER recomend doing that speed on a small bike anyway.
If all you can afford for now is a chinese engine, go with it for awhile then upgrade A.S.A.P. E-bay alway's has deals on them execpt to California thanks to the E.P.A. you can get a 60-80cc for about $150.00, mabey less, and sometimes even free shipping.
Get all the advice and help you can find for your first build. listen to the guy's on this site. Most of them know what they are talking about. And buy better nuts,bolts and mounting studs for that china engine. the ones they give you BLOW big time.
Good Luck on your first,
BIG RED.