yz426f wont start


9 replies to this topic
  • dirtbikemike1

Posted July 21, 2015 - 02:04 AM

#1

so i have a 2002 yz426f dirt bike and i bought it from a guy to see if i could clean it up and make it run better, it took forever to start it when i bought it and it runs great when u get it started, ive only been able to start it one other time since then so i decided to clean the carb. it was very dirty but i cleaned it really well and pretty much rebuilt the whole carb lol, and then put it back together and still no luck starting it, then i decided to replace the spark plug since the old one was burnt and i also checked the valve clearences too and they were in spec. after all that i still cant get it to start, its getting spark, and the carbs clean and the valves arent too tight either, oh and i also put fresh gas in it.
Any ideas why it wont start??? i have no clue.huh.gif



  • harmetp

Posted July 21, 2015 - 05:39 AM

#2

Seems like you must have let the 'magic' run out of the engine when you pulled the carburetor and these engines don't have much starting magic to begin with  :goofy:

 

But really, do you have an auto decompression cam or just the lever?  I've had much more success starting by kicking it over a few times with the decomp lever pulled.  

 

Things to check: 

 

1. pull the fuel line to make sure the carb is getting gas

2. is the carb float working right?  I had a carb fill the engine with gas because the float needle didn't seal or is the float needle stuck on the seat? 

3. did you leave everything set as it was or set it like the manual says? 

4. I have to make sure my idle is turned up some to get it to start.  After it's warm I can turn it down.  Otherwise lots o kicking and not so much starting.

 

I have not gone through my carb like you but probably need to so I may have quirks you don't have.  I'm not sure why these engines are so prone to flooding (valve overlap?) but it seems like they are rarely easy to start. 



  • grayracer513

Posted July 21, 2015 - 07:09 AM

#3

The starting drill:

 

http://api.viglink.c...troke_vid_a.mpg

 

http://api.viglink.c...troke_vid_b.mpg



  • dirtbikemike1

Posted July 21, 2015 - 11:42 AM

#4

I am getting fuel to the carb because after i kick it about 10 times fuel starts to slowly drip out the overflow tube, and i pulled the plug after i tried starting it and it was alittle wet



  • dirtbikemike1

Posted July 21, 2015 - 11:51 AM

#5

and i also have done the starting procedure many times with no luck, how far in should the idle screw be turned in and also how many turns should the fuel screw be turned out?



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  • grayracer513

Posted July 21, 2015 - 01:21 PM

#6

Remove the air boot from the carb, and turn the idle speed screw until it raises the slide enough to get a 3/32 drill under it.  That should be "close".  The pilot screw should start out at around 2 turns out from lightly seated.



  • dirtbikemike1

Posted July 21, 2015 - 02:00 PM

#7

Remove the air boot from the carb, and turn the idle speed screw until it raises the slide enough to get a 3/32 drill under it.  That should be "close".  The pilot screw should start out at around 2 turns out from lightly seated.

 okay thanks, ill do that and then see if i can get it running.



  • grayracer513

Posted July 21, 2015 - 02:13 PM

#8

If not, read the link below and have another look at your pilot jet.

 

http://www.thumperta...o/#entry6879695



  • dirtbikemike1

Posted July 21, 2015 - 06:46 PM

#9

it was close to starting, almost every time i kicked it over it was trying to start but it wouldnt start up completely and run, i kept messing with the idle and it seemd like it was getting closer and closer of starting but i still had no luck, i did this for about 2 hrs.



  • Super426

Posted July 25, 2015 - 12:56 AM

#10

Are you giving it any throttle while trying to start? The carb probably needs to be taken apart again and hot tanked. The small valleys in the can't get clogged and the staring circuit will get plugged...

This is how I start mine, now I have a brand new carb but if your carb is good it'll start this way fine. Make sure ur plug is dry. Push the kick starter slowly until it stops from the compression. Release slightly, pull comp release. Give it about a 1/8-1/4 kick, just to the point where it is past compression. Ratchet the kick lever all the way up from there and kick it hard. Do this until it starts. Let me know what happens, if it's hard to understand I'll post a video for you





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