426 pain in the @$$ to start

hey guys I got an 01 yz 426 and it needed an accelerator pump, so I ordered on, put it on and while I was in my shade tree mechanic ear tuning mode I decided to adjust my fuel mixture screw while I was at it because it wasn't very snappy. now my leg wants to fall off every time I start it cold, and if I start it after a couple motos and it has been on the stand for 30 minutes it runs like crap and is popping and bogging down. once I rev it up a few times and get it going finally its fine on the track, no hestitation or bog. I have the mixture screw set at exactly 2 turns out. it has an FMF power bomb header and some ugly FMF pipe that says titanium something or other. it takes a lot of throttle to take off when its doing this too or it will stall. but any other time its normal. thanks guys!

hey guys I got an 01 yz 426 and it needed an accelerator pump, so I ordered on, put it on and while I was in my shade tree mechanic ear tuning mode I decided to adjust my fuel mixture screw while I was at it because it wasn't very snappy. now my leg wants to fall off every time I start it cold, and if I start it after a couple motos and it has been on the stand for 30 minutes it runs like crap and is popping and bogging down. once I rev it up a few times and get it going finally its fine on the track, no hestitation or bog. I have the mixture screw set at exactly 2 turns out. it has an FMF power bomb header and some ugly FMF pipe that says titanium something or other. it takes a lot of throttle to take off when its doing this too or it will stall. but any other time its normal. thanks guys!

mine did this. I knew the valves were on there way out so I kept ridin it until it wouldn't start anymore. then rebuilt engine.

check all ur valves have correct clearance. then if u can remove ur carb, clean carb and tell me ur jet sizes and elevation. do a compression test, then a wet compression test. tell me ur compression readings for both tests. and obviously give airbox and filter a good wash.

tell me all ur jet sizes, pilot jet, main jet, starter jet, leak jet, main and pilot air jets and needle type and clip position

Yeah, sounds like valves. Mine used to not like starting, but after changing the pilot jet it starts first kick most times. If you leave it setting for months at a time it will always be a bitch to start. I let mine set for 2 full months and it took 12 kicks before it finally came to.

 I decided to adjust my fuel mixture screw ... now my leg wants to fall off every time I start it cold, and if I start it after a couple motos and it has been on the stand for 30 minutes it runs like crap and is popping and bogging down.

 

 

Therein lies your problem, I would guess.  80% of the things that make a 426 hard to start are related to an improperly set up idle circuit. 

 

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