The quad in question is a '03-04 (I don't know b/c it's not mine) Yamaha Kodiak 450. The only mod I know of is a performance pipe.

As my friend explains it; It hasn't been running right. Anyway - he let a couple of fellow hillbillies work on it - they were sure it was the float. Which they took apart the Carb, replaced the float, and cleaned out the jets, put some octane booster in the gas - and gave her a try...

That was a week ago. I just got on the problem yesterday and cannot attest to their craftsmanship - that's why I come to the genius of this forum - EXPERTISE.

It won't run without the choke on (halfway or just under), I 'cleaned' the plug, adjusted the mixture screw, while I idled it. I haven't let the bike get hot for fear of causing another problem... What we're getting is a serious backfire. It doesn't get the fuel/air I think as the mixture screw, even with the air filter pulled doesn't seem to fix the problem at either extreme. But, even choked, the backfire and occasional smoke cause serious concern... should we dealer it, or do you have any suggestions?

 

Don't dealer it. They will end up ripping you. Start with simple stuff and work your way back. Plenty of gas, fresh oil/gas, fuel lines clear, spark plug(you can figure out a problem by the appearance of the plug), battery connections, etc... What did your plug look like when you cleaned it off?