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06 yz450f compression issue

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Hello everyone, I have a 2006 yz450f that seemed to lose compression out of nowhere. I had started up the bike then shut it off with no issues a few weeks earlier. But now when I go to kick it over there’s no resistance the kick starter feels likes it’s going through butter. Any ideas on what the issue is? Any help is greatly appreciated.

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There is no way to tell unless you do a leak down test. You put the bike on top dead center compression stroke then add air and see where it comes out or if it holds the pressure. You can also take off the top valve cover and check to see if there is any clearence in the valves. 

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Both my old '06 and my '15 do/did this on the regular, kick it thru couple few times then back to normal....I always assumed the decomp button hanging out. My last bike 20 yrs ago was a cr500 so I'm quite used to kicking a bear, so when it rolls right thru it's very noticeable.

 

Edited by wetneck

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It's either a sticky valve that is not sealing up all the way, or as already mentioned the auto decomp device on the exhaust cam is sticking.

Pull the valve cover off and check the valve clearances, and check auto-decomp device on the exhaust cam to make sure it is not bound up.

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