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Kx250braaaap

426 pain in the @$$ to start

5 posts in this topic

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!

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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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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

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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.

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 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.com/api/click?format=go&jsonp=vglnk_14222863856076&key=fd4d0c8927dbf2331e83bbda32ac7c21&libId=c9a342b2-c35b-4433-bc33-fd74285062dd&loc=http%3A%2F%2Fwww.thumpertalk.com%2Ftopic%2F378677-common-threads-look-here-1st-mods-maintenance-common-issues-and-faqs%2F&v=1&out=http%3A%2F%2Fwww.thumperfaq.com%2Fjetting.htm%23PJ&title=Common%20Threads%3A%20Look%20here%201st!%20Mods%2C%20Maintenance%2C%20Common%20Issues%20and%20FAQ%27s%20-%20YZ%20400%2F426%2F450%20-%20ThumperTalk&txt=http%3A%2F%2Fwww.thumperfa...%2Fjetting.htm%23PJ

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