Need some tips. yz426 wont start after cam swap and carb clean

4 replies to this topic
  • mdemyers

Posted March 01, 2014 - 05:40 PM


I recently did the hot cam swap and cleaned the carb out on my 2000 yz426.


After putting everything back together I can't get it to fire. It seems like it isn't getting fuel.


I just keep kicking and kicking and I get nothing. Doesn't even sound like it wants to start.


before this work it ran 100% fine, it just wouldn't idle right(why I cleaned the car), but trail running it had no problems as long as you didn't allow it to idle for more than a few seconds.


I do have spark. That is one thing I am certain of. I pulled the plug and placed it in the boot. Closed the garage door and could see a good spark and it is a new plug also.


Any one have any tips or know what I'm missing here?

  • mdemyers

Posted March 01, 2014 - 05:44 PM


Also I have quadruple checked the timing of the new cam install and also the valve clearances on both sides. All are right on target.

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  • grayracer513

Posted March 02, 2014 - 12:27 PM


What cam did you use?

  • mdemyers

Posted March 02, 2014 - 03:38 PM


Hello again.....seems like I'm full of problems and you are full of solutions.


Ok So I logged in to make an update, but thanks for the quick reply.


I used the hotcam exhaust cam made specifically for this bike.


Anyways. After taking everything apart again I re-shimmed the bike to exact middle of the specs on the intake and .22 on the exhausts (hotcams recommends .20, but didn't have enough shims.).


I got the bike to start up right away and run! Big success for me.


I think I had the cam chain tensioner too tight. I was unaware that if you screwed it out all the way it would stick until you unset it. I didn't know this previously.


Anyways I am still experiencing poor idle. It had this problem before I did all the mods. It had been sitting for a while before I purchased.  I could visibly see the light at the end of each jet after cleaning (I could see it before also). The only real problem I found was a disintegrated accelerator pump diaphragm which I replaced, but I am under the impression that only came into play while running it.


Any suggestions on what to chase down next?

  • grayracer513

Posted March 02, 2014 - 06:58 PM


Regarding the pilot jet




Another common mistake that is made by those not familiar with the Keihin carb is that the vacuum release plate on the engine side of the slide can be assembled upside down.  The Square end with the hole near the edge needs to be down, even though it looks a little like it should be the other way.  The very thin seal between the slide and plate can be a problem, too, if damaged.  If you find it swollen out of shape when you take it apart, let sit out on the bench overnight; it will probably shrink.

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