CRF's Only Forums

Ok, I've got an issue and I'm hoping someone has some direction. Bike is an 08 CRF150R that I got for my boy last year. I purchased it with a hanging idle thinking the carb just needs cleaned. NOPE. Starting with idle high enough to start, bike seems to run well until I blip the throttle. Idle hangs and stays. If I drop the idle while its hanging, bike usualy dies and will not start until I raise the idle again. It acts like this right after I start it and and does not get any better if the bike is warmed up. Bike runs great otherwise.

So far I've gone completely through the carb and installed carb kit including new slide gasket and mid body gaskets. Tried every pilot from 38 to 50 with stock needle while trying to adjust fuel screw for correct idle. Fuel screw is an R&D flex jet and has the spring, washer and o-ring in the correct order. Did find one intake valve with zero clearance so I re-shimmed it. Figured that had to be it. NOPE. Have checked valves multiple times and they didn't move after re-shim. Tried a brand new carb. Installed JD jet kit. Cannot find an air leak but replaced carb boot anyway. Installed an FMF snap and the bike already has a flywheel weight. I've read both of these can help but not on mine. TPS is in spec and adjusted correctly. Unplugged has no effect.

As a last resort I tore the head apart to inspect valve-train and the right intake had some cupping so I sent the head to Ken for his KW valve job. Also putting in a new piston and cam chain while I've got it apart. Hoping this will resolve my issue but I'm not holding my breath. So while I'm waiting for the head to come back I figured I would ask if anyone has solved this hanging idle problem by doing something other than what I've already tried. Sorry this is so long but I've never had a bike act like this and I'm getting to the end of my rope. And budget. Any help would be appreciated. Thanks.

You have lubed the throttle cable and made sure it is returning the throttle plate to the idle position? Make sure the throttle tube isn't binding as well.

You have lubed the throttle cable and made sure it is returning the throttle plate to the idle position? Make sure the throttle tube isn't binding as well.

Thanks for the reply. I knew I would forget to add some things I've tried. Yes, I've replaced both throttle and hot start cables. The throttle does snap shut each and every time.

Well it looks like getting a valve job from Ken did the trick. I still have a slight bog to tune out but now the bike will idle normally and return to idle after blipping the throttle. Thanks Ken and CRFSONLY for the valve work done on my head. Highly recommended.