I have a 1989 yamaha warrior and i put in a web cam .430 lift cam, .430 tension valve springs, black diamond valves, port and polished head,the cylinder is bored .040, (now a 355), weisco 10.25:1 compression piston, k&n filter, 6 one inch uni filtered vents, Fmf power bomb header, fmf megamax 2 exahaust with 9 discs and i was wondering if anyone else did mods like this or similar ones what size of main jet should i use? My quad uses the mikuni 36mm BTM carb, i ride at 860 feet above sea level. any help anyone can give me will be greatly appreciated thanx. Additional mods include holeshot xtc's front and rear, itp .190 offset rims on the rear, non-offset in the front, triple rate spring on the rear shock, 4 inch (total) front wheel spacers, custom painted a-arms, tag x5 bars, 14-41 gearing, twist throttle, polished levers, master cylinder cover and clutch cover, ebc dirt digger clutch system, Dg nerf bars and a-arm quards, perfex skid plate, kimpex tether, custom painted foot rests, all wires and cabled have been wrapped with coverings, purple taillights, all plastic covers (flywheel cover, carb side plate, chain gaurd, rear brake master cylinder cover) have all been custom painted blue. Black leather seat cover, shockwears. All the work has been done by me with some help by a friend of mine.

 

My 87 has a few simular mods but not as many. With my white bro PM it runs rich at 1,200 feet with the stock 145 in it. Start off by putting in a new plug, go ride, and see what it looks like. Also, if you quad backfires it is running really lean.

 

Thanks for the advice but right now with the header pipe, the megamax 2 silencer, k&n filter, modified air box it runs perfect with a 150 so im definately going to have to go up from that, probably a 155 or 157.5 thanks for the input though, Does anybody else have a suggestion?