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Cam Tension


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Might be too basic, but I've been wondering this for some time. Why?!?

 

Disclaimer: I'm a definite engine novice...just recently went from menace to wrench-turner ;):lol:

 

 

So: Why do I have to periodically tighten the cam tensioner? -and- Is the "rattle" I hear just before I tighten it, the sound of the valves not closing/oping completely?

-Material from the tensioner wears?

-The cam is wearing?

-Just cause?

 

A friend gave me an adjustable tensioner, so it's pretty easy now. But seems to me isn't something that should be adjusted often. ***I'm tightening it for the thrid time this weekend [based upon the service manual specs - finger tight then 1/4 turn]*** (about 50k miles on it).

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Might be too basic, but I've been wondering this for some time. Why?!?

 

Disclaimer: I'm a definite engine novice...just recently went from menace to wrench-turner ;):lol:

 

 

So: Why do I have to periodically tighten the cam tensioner? -and- Is the "rattle" I hear just before I tighten it, the sound of the valves not closing/oping completely?

-Material from the tensioner wears?

-The cam is wearing?

-Just cause?

 

A friend gave me an adjustable tensioner, so it's pretty easy now. But seems to me isn't something that should be adjusted often. ***I'm tightening it for the thrid time this weekend [based upon the service manual specs - finger tight then 1/4 turn]*** (about 50k miles on it).

 

 

it wasn't that long ago that all bikes had manual adjusters for the cam chain, we did them with every tune up. The cam chain is a roller chain just like the drive chain and as they wear the slack must be taken up. The tension on the chain itself is on the opposite side as the tensioner, I don't know what makes the noise but I think it's the chain riding up the sprocket teeth when it too loose or slapping the chain guide. the vales are not effected by the chain being a little loose.

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Thanks for the input. I was missing the cam chain part - it's been well over 10 years since I've seen the inside of an engine, something that was only a hand-full of times to begin with.

 

I'll have to look in the service manual; maybe I missed that it's supposed to have already been changed.

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Overtightening the chain will stretch it, often unevenly. It also increase wear on the tensioner and rubber guide, which usually require top end removal to get to. You should also ceck the sprockets for wear. But if you're lucky, a new chain is all that's required. AFAIK there is no typical wear schedule when it comes to cam chains; they can be gone in 20,000 miles or last 200,000 miles, depending on luck and (ab)use.

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Overtightening the chain will stretch it, often unevenly. It also increase wear on the tensioner and rubber guide, which usually require top end removal to get to. You should also ceck the sprockets for wear. But if you're lucky, a new chain is all that's required. AFAIK there is no typical wear schedule when it comes to cam chains; they can be gone in 20,000 miles or last 200,000 miles, depending on luck and (ab)use.

 

 

Not true, the reason the cam chain tensioner is automatic now is so you don't have concern yourself with it not because the chain doesn't stretch much. The typical tensioner has an inch of throw and that is a lot movement when you look at the fact it is pushing a solid arced guide that is neatly the length of one side of the chain.

 

The question was how often the cam chain should need to be adjusted with a Manuel adjusted and my answer may have been a little ambiguous? depending on use (street) 3000 to 6000, track when you start to hear it.

 

How? This is easy on a stock bike without the exhaust noise but I would break them loose and loosen it first so you get a real good idea of what the chain sounds like and the run it in until that noise goes away. Just at the point of silence is a little too tight, you want to hear it just a little. This will take some practice and is all done at idle. one small thing to add is the cam chain was always the last hing I did on the tune up because a ruff idle from vales, throttle body / carbs, old plugs being out of adjustment or worn will make the cam chain louder as the engine struggles to idle.

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..... one small thing to add is the cam chain was always the last hing I did on the tune up because a ruff idle from vales, throttle body / carbs, old plugs being out of adjustment or worn will make the cam chain louder as the engine struggles to idle.

 

Interesting. I've been wanting to through back the tank and dive into [part of] the engine - but not quite there yet. Never thought about valves or plugs; although it makes sense.

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Not true,

 

I'm curious to what isn't true? I don't have any objection at all to the rest of your post, to which I agree fully, but I do hope you will take the time to explain exactly what was/were wrong in what I wrote so that I can avoid making the same error(s) again.

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Not true,

 

I'm curious to what isn't true? I don't have any objection at all to the rest of your post, to which I agree fully, but I do hope you will take the time to explain exactly what was/were wrong in what I wrote so that I can avoid making the same error(s) again.

 

 

it was actually your earlier post that I objected to

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Something is wrong if you constantly have to tighten the cam chain - you're either overtightening it, or the chain is overdue. Whatever it is, I'd find out before it throws the chain and cost you a fortune.

 

This one, As i outlined adjusting the cam chain with a manual adjuster is a common and frequent thing. Part of the reason is the infinite adjustment of having the threaded rod vs a ratcheting mechanism, finer adjustments. The 07 ZX6R was a great example of the mechanism with too course a tooth count, they would make horrible cam chain noise before they self adjusted. The first few I took the adjuster out to make sure it wasn't stuck but one day while standing next to a bike that was very loud it adjusted to silence. Once I was aware of it I would pay attention to the bikes that were loud and they would all come back from the next ride quiet.

 

Another thing is that I have never changed a cam chain because of wear. I change the cam chain as a matter of course when I redu a motor for the track or any of the new dirt bikes. I have no idea how far one will go but I have seen bikes with over 200,000 miles and all the original parts. We ran the last fleet for three years and I ended up with the highest mileage bike at 44,500 track miles. On my KX 250F I got it from team green as someones race bike and rode it for three years before I figured it was time to take a look. I was going to change the valves and put a six speed kit in it. After I got it out I realized the crank was done, most of the trans and the output bearing was ready to explode. After I got it back together I realized it must be done when I got it because I had never heard it so quiet. Even with crank and trans bearing ready to fail the cam chain wear was imperceptible, yes I changed it. More because you need to split the cases to do it and I hate doing anything twice, cheap insurance.

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