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Cam Chain Stretch ?

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Hi.

'04 crf450

I got kibble valves and springs with probably 50-100 hours on them now. A little while ago after a race there was a terrible noise from the engine. Turns out the spring on my chain tensioner failed and there was no tension on the chain. The chain was loose and rattling around. No other harm was done.

I made a manual tensioner out of the old tensioner and used that. After a few hours with the manual tensioner there was a bit of a noise coming into the chain again. It looks to me like my chain might have stretched a little. Does this happen? Would this have caused my stock tensioner to fail? Anyone come across this before. Also I didn't tighten the manual tension very stiff. I though I just tightened it enough to take the play out of the chain. Anyone know if it's easy to stretch the chain with a manual tensioner?

And finally, does anyone know if using the stiffer springs with the kibble valves gives the cam chain extra grief. And would that have possibly caused the chain to stretch. Are there any chain measurements that I can check ?

If anyone can answer any of my questions I'd be very happy.

Many thanks

Mick.

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The chain will stretch a very small amount. That's why the chain tensioners, auto or otherwise, are there. The springs will add more stress to the chain, but not significant enough to justify the reason for the stretch. I think you need to look more to your modified tensioner. You probably should put an auto tensioner back in it.

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I had the exact same problem with my 2003 450 and I finally got an answer after my cam chain skipped a tooth twice, it may seem like your tensioner is bad your cam chain has stretched and it is just minimal but it is enough to slap against the tensioner and back it off, it is made to stay in if you put enough presure on it, replace you cam chain, it will take a few minutes once you get the flywheel off and you willl not have any other problems.

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The cam chain sliders could be wearing too...When you set the tension with a manuel tensioner, you have to make sure the thing is at top dead so that the cams arent trying to push either way and artifically give you tension on the chain.

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To set a manual tensioner apply some pressure to the chain so it won't skip, @ TDC on compression stroke, then turn the engine over in the direction of rotation while tightening the tensioner bolt with your fingers. Get it finger tight, but don't reef on it, then back it off a little bit I usually go one to one and a half flats on the bolt head. Lock it down and safety wire it so it can't back out. This is how I set all the manual tensioners on my roadrace engines. It's best to turn the engine over through one of the inspection plugs with a wrench as the kicker could spin it to quick causing the chain to skip before the tensioner is set.

I would also suspect like other posters have said that it's time for a new chain, and have a good look at the chain guides.

:banghead:

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my 04 did the same thing. new chain and tensioner fixed it right up....the guides are fine. dont worry about them.

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Thanks for all the help.

I decided first thing was to replace the chain. When I took it out each link seemed quite stiff, much stiffer then the new chain. When I put the new chain in, using the manual tensioner, the bike sounded great again. And a ticking noise that had developed over the past month or two at low idle went away. I didn't realise a chain would do this. The bike never ran low on oil or anything.

Anyway, bike is happy and I'm happy.

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you have to make sure the thing is at top dead so that the cams arent trying to push either way and artifically give you tension on the chain.

I noticed. I got a fright when I turned the engine and felt the chain tightening and loosening.. For a second I though something serious was up at the bottom end of the chain. :banghead::applause:

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