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2009 CRF450R Cam Chain Going Bad?

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A buddy of mine drooped his '09 450 because the engine is making a grinding noise. It seems that the noise is coming from the cam side and the chain might be loose. He said it has a new tensioner so that's probably not the problem. Is there a way to check the chain to see if it has stretched?

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Pull the valve cover and check tension on the can gear or pull the entire chain and visually inspect it. Make sure he installed the tensioner correctly. An incorrect tensioner install can stretch a chain in a matter of minutes. Does the noise seem to get quieter under any circumstance?

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The cam chain don't stretch. And if the chain was loose from the tensioner not working properly for whatever reason then you'll be able to hear it making a slapping noise. Either way I'd get down to the bottom of it before letting her rip again

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Also is there a reason he replaced the tensioner and not the chain? The chain is a wear item and they do get weak. If that thing snaps he going to have to go through that whole motor is I'd definitely replace that asap anyways

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The cam chain don't stretch.

That's odd. I've replaced several cam chains and every time I replace one the old chain is a good .040-.060 longer than the new replacement? I guess I'll get technical. The chain itself don't stretch. Each individual pin wears causing the chain length to wear outside of their service limit. In very simple understandable terms......the chain "stretches"

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I assume he meant it wears, but doesn't stretch. Just like a drive chain...

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I'm sure your right I shouldn't have come on so hot. Bad morning thanks to the parts guys at the auto parts store haha. Most less mechanically experienced guys usually just use the term stretch instead of pin wear

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I recently spent some time with the guys down at the machine shop trying to diagnose the missed timing on my 05. I learned a lot. 

 

1 - Cam chains do wear, but it's pretty minimal, and unlikely that it's enough to cause a timing issue.

 

2 - the cam-sprocket bracket (the piece the cam sprocket screws into) is pressed on, and with a big enough issue can and will slip slightly. This will cause major issues in getting the timing right, because the marks on the sprocket will line up correctly, but the cam lobes will not be in the correct position.

 

My guy recommended getting another cam (which I have) and comparing the two side by side. Not sure if you have access to a friend with the same bike as you, but I'd check.

 

Also, replace your cam chain.

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A loose cam chain sounds like bolts bouncing around in the engine.

A slipped cam gear with offset timing sounds like a bike that isn't mapped correctly and it usually won't idle (popping, dying, hard to start etc)

Grinding noises are usually bearings going out.

 

Personally I'd start out at the cam bearings just to see if they roll smoothly and not feel gritty or make a whirring noise when spun, and while the cam is out, roll the cam chain over your fingers to see if there are any kinks. I'd check the stator/flywheel just in case there is a loose bolt backing out and grinding on the flywheel (seen it happen), if there isn't anything by then,  I'd tear down the engine and check the cylinder, and each bearing until I found the culprit.

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