hey there, well, i got back fire though the carbs which is blowing the carb boots off. its a pain fixing it all the time. but here is what i know. 2002 raptor- never had problem stock
had valves adjusted, the next day i had hmf pipe and carbs rejetted.
now when i am starting the machine if i hit the gas it will create conditions for back fire though the carb, and there goes the carb boots.

so one i thought they "Yamaha" fixed the carb boots on the 02's

two how do i fix this problem?

any in put would be a great help
thank you

 

Here is a couple things to take into consideration. This is what Yamaha said to me a while back. First make sure you allow proper warm up time before you start riding(personally I rarely do and I havent had a problem). second check and make sure your idle speed isnt set too low. Last make sure you Idle mixture screw isnt set to lean.

 

who adjusted your valves? make sure that they're adjusted properly. the intake valve might be slightly stayin' open.

 

the dealer adjusted the valves, and i did turn the idle up just to make sure. so maybe ill be lucky and it was the idle settings. As far as fuel air mixture.... its perfect, or as close to perfect as it can be. The cycle shop i took it to have it jetted specializes in jetting. They have all kinds of technilogical gizmos that they hook up to the bike that gives them reading at different rpm's to tell if rich or lean bla bla bla

 

Take the spacer out of the clamps and you will be able to tighten the clamps more.
Option #2: put regular hose clamps on.

 

Pick up some real hose clamps and replace the stockers. Put them on properly and the problem is usually solved if everything else is right.

 

Look at your clamps to see if they're tweaked.
Only tighten them till they touch the spacers, If you continue to tighten them they'll bend & be useless.

 

Most importantly, DITCH THE STOCK CLAMPS!!

Those cute little things are good for nothing on an ATV, and should have never been used from the factory. A friend of mine bought one of the very first Raptors and had that problem constantly and it baffled the dealer, so an actual Yamaha of America rep flew out from CA just to tell them to replace the stock clamps with some real automotive ones. This guys Raptor actually split the boots open a couple times!