heres the deal. ive been working on my freinds blaster and i absolutely hate it. when i got it i had to bore it over becausea there was a detonation. another problem was a hole causing an air/oil leak in one half of the cases.

replaced one half of the case, new piston kit, new crank, and bored. roughly 600 dollars with all the stuff. it has an aftermarket exhaust system, k&n airfilter, (no air box) , and im pretty sure the jet is the original. the idle SPEED screew is missing but yet it still idles. it doesnt smoke too bad so i dont think its a leak in the case, if anything between the cylinder and the case. is this a guarenteed air leak or a a possible carb prob?

 

u wont be able to tell when it has a air leak my banshee used to have a bunch of them it just ran really good for a short amount of time but the motor back together and rig up somethink that clamps to the header with a gauge and put air in it and it will tell u if it holds air... i think it needs to hold 6 psi for five mins if it does then its not a air leak

 

If it has stock jets with all those mods that is without a doubt your problem. REJET!