On my 2002 yamaha 660 raptor a mixture of air and fuel sprays out the intake (rear) of the carburators. I have the air box off and when I give the enging some throttle, this happens. It happens mainly when the engine is accelerating. The engine runs lean obviously because of the fuel that is escaping out the rear. Would anyone kindly help me out. Thanks a lot

 

dan your prob is your tryin to fix up a piece of *** with no hope at all....just kiddin somebody help te poor kid out

 

Have you checked the intake valve clearance, or if the cam has been out...it could be off a tooth.

 

yeah.. i had a feeler guage between the rocker and the tappets (where ther should be a few thousands of clearance) and they are not touching. The top end of the motor has never been taken apart and all the timing has never been messed with.. I am really stumped.. any other thoughts?? thanks

 

also the air fuel mixture sprays out both carbs. It doesn't really seem to spray out nearly as much when the motor is running at a constant rpm.

 

you'll have that

 

Wow this is a good one. The 660 has some kind of rubber boot on top (under the 2 covers) that seems to work the carb slides up and down with of a vacuum from the engine. I don't understand how it works but maybe the rubber boot is split or if it does work on a vacuum maybe the vacuum hose is split or has come off.

 

The only way the flow will go backwards, is if the intake is left open, while the piston comes up in the compression stroke. Is it posible theres a build up on the intake valve, or something holding it from shutting completely.
Try a compression test, and see what it is.

 

Thanks guys.. i will try a compression test and see what happens then.. I dont know if the compression reading will be accurate because i think there is a decompressor for idleing. But i will try it. I was also thinking possibly a chippped intake valve? If anyone has any other ideas I will appreciate it.

 

I understand what you mean with the rubber boots now.. I haved inspected them and they are good.. all hoses are in place when it sprays the fuel as well