Yz450f problem

Hi, I just bot a 2006 Yz450f last week. I was riding it today and it was running great, but then it did not want to idle, so I kept on the gas and started driving it to my garage. When I was going to start to slow down, right when I got off the gas it died on me. So I let it sit for about 20 minutes and tried to start it again, I kicked it over about 20-25 time and it didn't start. I thought it just over heated or something but I wasn't riding very long. Please let me know what you thing it is.

Check/replace the spark plug. 


Do a compression test. 

My guess is in the jetting.

I would check valve clearance to since you just bought it used.

"Compression tests" are useless on an engine equipped with automatic decompression, wouldn't you say? :cool:


Verify that you have spark.


Check the valve clearances and the cam timing.


Open the carb and physically check the jets and passageways for any obstruction, especially the pilot (or, "slow") jet.



Should there be an ideal number anyway? If not couldn't you disable the auto decompression and get a accurate number?

Too many variables.  In the first place, the reason the 426 had a manual compression release on it was because it is next to impossible to crank a healthy one through a full compression stroke without it.


Even in the car world, a compression test is best used to identify cylinders that have significantly different compression than the rest in the engine, so they don't amount to much on singles.  An '06 that runs perfectly well may only muster up 90 psi or so on a conventional test.  But it wouldn't be hard to start just because of that, either.  


The way to determine how good the compression sealing is is to run a leak down test on the engine.  

Out of gas ?

Jumped timing probably. My 06 YZ450F did that too. The cam chain was stretched. So I'd check cam timing like grayracer513 said.

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