Hey guys. I’m out of ideas and hoping someone can help. I have a raptor 350 that won’t idle when it gets warm. It almost sounds like it’s missing a spark randomly and shuts off. Starts right back up. If you give it a little throttle it runs fine. If you just tap the throttle it idles high and then Boggs down and shuts off. Changed the CDI, Stator, Coil, plug. Carb has been ran through a ultrasonic cleaner twice and got a rebuild kit. If I turn the idle up it doesn’t do anything until I rip the throttle and then it idles super high. I cannot for the life of me figure this thing out. Runs fine on the top end.

 

Sounds a lot like the usual Yamaha cracked inlet manifold problem. Have you checked this? Also check the diaphragm in the carb for splits, and I find a good blow out of jets and passageways in a carb works, not sure that ultrasonics do much more than loosen dirt. Make sure the butterfly lever is hitting the idle speed adjuster screw after you open and close the throttle, a sticky spindle can cause those symptoms. Finally, check valve clearances, on the grounds that you have done everything else, though closed up clearances usually leads to bad starting on Yams.

 

Not only check for cracks in the diaphragm but make sure it is super soft, no stiffness at all as ethanol is hard on them.