426 pain in the @$$ to start


4 replies to this topic
  • Kx250braaaap

Posted January 20, 2015 - 06:14 PM

#1

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!



  • jakeh_16

Posted January 22, 2015 - 01:42 PM

#2

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.



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  • jakeh_16

Posted January 22, 2015 - 01:45 PM

#3

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



  • DunmireD001

Posted January 25, 2015 - 07:51 PM

#4

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.

  • grayracer513

Posted January 26, 2015 - 07:33 AM

#5

 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. 

 

http://api.viglink.c.../jetting.htm#PJ







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