426 kicks over no lever

5 replies to this topic
  • Type Gendy

Posted April 03, 2008 - 04:19 PM


So i pulled my bike out last week and fired it up. It ran briefly then it stalled. I was satisfied at that point and put it back in garage

I went to start it last night and now it kicks thru all the way without the decomp lever. There is some resistance , its now free, but i can kick it all the way thru without the lever? Whats going on here?

the lever still feels normal and i can see the actuator on the motor moving up and down. When i hold it in then it kicks over freely like it should

  • jrny426

Posted April 03, 2008 - 04:27 PM


sounds like something is sticking ,cable,or the lever on the valve cover ,perhaps something internal if like you say visually everthing is good,I'm sure someone here can help but I've never had this issue

  • jbrooks26

Posted April 03, 2008 - 05:07 PM


There are many possibilities. First off, how long has this bike been sitting? If it has been sitting for quite some time then it may just need a light coat of oil on the cylinder walls. The oil helps build compression as well as lubricating the engine. Second, you could have a decomp mechanism that is not releasing completely and allowing the exhaust valve to stay open slightly. Third, you could have bent a valve somehow. Or you could have a valve shim that has slipped loose and is not sitting flat in the lifter cap which may be opening a valve early or not letting it close. There are other possibilities, but this should get you started.

Does the bike start and run? Does it make any noise while it is running? I would start with a leak down test to point you in the right direction. You basically pressurize the cylinder with compressed air holding the engine at BDC and listen for an air leak. Air from the exhaust means you have an open exhaust valve. Air from the carb means an open intake valve. I hope this helps.


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  • Type Gendy

Posted April 03, 2008 - 05:51 PM


Thanks for the thorough reply, that definetly gives me some places to look

Bike has been sitting since oct/nov. Fired up after a few kicks last week. Then it stalled cause it was cold and i didnt try it again because it needed fresh gas. Should i try some oil down teh spark plug hole at this point?

Cant imagine it bent a valve cause it ran like a top when i put it away and started after the long winter rest... But havent started it since it did this. I dont think it would cause it doesnt take much to kick it. Is there a way to check the decomp lever without disassemblin the head?

  • grayracer513

Posted April 03, 2008 - 06:27 PM


Should i try some oil down teh spark plug hole at this point?

Yes. ATF or Marvel Mystery Oil (auto parts store). About a teaspoon in the top, crank it through a few times, put the plug back. Add a teaspoon to the next gas tank for good measure, too.

  • sirthumpalot

Posted April 03, 2008 - 06:30 PM


This has happened sporatically to many yz426 owners, search the threads here. In every case I've seen, including with my own bike, put in a new spark plug (if necessary) and kick it a few times until it fires. When it fires the problem is mysteriously solved. This happens to my 426 100% of the time if I put carb cleaner into the carb while it's still on the bike, instantly zero compression but it fires easily when kicked and instantly the problem is gone. Maybe yours just got a pile of gas or something. Give it a whirl. :prof:

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