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Dick Falcon

A few Q's for Grey and the other Yzf gods

12 posts in this topic

Ok guys ,Ive got a 09 yz 450f.i have 21 hare scrambles on the bike.latlely its running hot ,and it getting harder to start.im thinging it top end and cam chain time.What do you guys think??

k

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Get an Iridium spark plug cr8eix fill with new coolant unless you Want a piston go get one OEM pistons will fit right for another 21 hare scrambles if you are doing it again

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i just put a new plug and engine ice ,its just not running right.how can i tell if the cam chain is stretched??

Just be on the safe side and replace it.

harder starting could mean the valve clearances are out of spec. check the valve clearances and re-adjust if necessary (since you will have the valves off anyway if you swap out cam chain.)

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One good visual indication of the wear on a cam chain is how far it will curve laterally.

They are so cheap, though , that you should just install one as a routine item every season or so.

A leak down test will tell you a great deal about the condition of the top end and what it really needs.

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I've found that hard starting seems to point to a valve issue. Cam chain problems could be tied in to that.

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Harder to start and hot running also opens the possibility of dirty jets/passages.

It will usually also show that through a decel. popping, but cleaning the carb/jets also a consideration.

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tell me what you find when you are done because i have an 09 too and it starts first kick only when warm

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One good visual indication of the wear on a cam chain is how far it will curve laterally.

They are so cheap, though , that you should just install one as a routine item every season or so.

A leak down test will tell you a great deal about the condition of the top end and what it really needs.

What do you recommend for a replacement? OEM?

I'm guessing this isn't like changing a drive chain where both sprockets should be changed at the same time?

thx

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The manual says to change all the sprocket with it, but that means both cams and the crank. So, no, only the chain unless one of them is really terrible.

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