Cam Chain Tension

YamahaRider

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Hi Everyone
I Installed a new head gasket in my 82 Seca 400 I have everything reassembled the timing marks are all lined up. My question is when I bring the left piston up to TDC the intake camshaft kicks counterclockwise and there is a fair amount of slack in the cam chain does anybody know if this is ok or is this a problem? Any help with this would be greatly appreciated.
 
There really should not be noticeable slack in the cam chain; it should have two plastic guides, with one compressed by the tensioner device. Make sure those are properly installed. I'm not quite sure I know what you meant by the camshaft kicking though.
 
Thanks for the reply I was thinking that there shouldn't be any I guess I will have to look at the tensioners to see if I installed them correctly Thanks again
 
Do you mean it kicks by turning the piston to TDC and not past, and the force from compression kicks the piston itself, and all, backward by not getting past TDC?
I am missing a camshaft and only have SOHC, but from what i learned all cam chain slack should be at the tensioner side for the tensioner to do it's tensioning job without affecting the timing marks which you have lined up when assembling.
 
Do you mean it kicks by turning the piston to TDC and not past, and the force from compression kicks the piston itself, and all, backward by not getting past TDC?
I am missing a camshaft and only have SOHC, but from what i learned all cam chain slack should be at the tensioner side for the tensioner to do it's tensioning job without affecting the timing marks which you have lined up when assembling.

I am turning the engine over by the ac generator bolt with no spark plugs in it what is happening is the lobe on the intake cam starts to go by the valve shim the force from the valve spring causes the cam to go counter clockwise and as a result of that the chain becomes somewhat slack and if you continue to turn the ac generator bolt a little further the chain tightens up and is good all the way around until you get to top on the left cylinder again.
 
Hmm.. I'll offer what I can about cam shaft behavior on a DOHC. When I was adjustiving the valves I did notice that the cams love to just 'fall' if you will. When moving the cams around I would be rotating the engine via the generator bolt and they would move well then suddenly 'fall' as the engine rotated. I didn't think much of it, and the bike runs great.

If you need to get the cams/engine into a very exact position you can use the socket connected to a non ratcheting rachet(if that makes sense). I don't know its technical name, but I had a big ass breaker bar I was using when I had to keep it in place. Was pretty easy.
 
Hmm.. I'll offer what I can about cam shaft behavior on a DOHC. When I was adjustiving the valves I did notice that the cams love to just 'fall' if you will. When moving the cams around I would be rotating the engine via the generator bolt and they would move well then suddenly 'fall' as the engine rotated. I didn't think much of it, and the bike runs great.

Sounds like a good explanation. And the fall. Assuming you are turning the engine counter-clockwise (forward) and it might only mean that it turns out your valve springs are good. Shim should be riding/making contact with cam throughout. Is the slack between the two cam sprockets then? I would assume when you say that it tightens up again, and there is absolutely no slack between the 2 cams then not much of a problem. I won't comment further since mine's SOHC.
 
When I replaced my head gasket, there was no slack once the two tensioners were in and correctly tightened. I'm looking at the Yamaha service manual, and it confirms there should be NO slack once your sprockets are installed.

The front cam guide is the long tongue shaped tensioner - it provides a constant pressure, and should fit into the small indentation in the inside front of the barrels. After it's in, install the sprockets and make sure all your timing marks are aligned. Once they're all in, the rear tensioner is installed from the outside (with your new gasket, if you have one), and is tightened with a torque wrench to the correct spec (11 lb/ft).

Then, play with the engine, and there should be no slack. You don't want your chain slackening and then tightening at 8000 rpm - you'll need a new engine in no time.
 
I promised not to chime in on this subject having a SOHC, sorry! Assuming the chain guide is ok and tensioner is properly installed, correct me if this is wrong but turning the engine by hand can hardly replicate or simulate the operation of the valvetrain at idling speed and the "fall" as described (turning by hand) would force the cam along momentarily to make it seem like there is slack when at engine speed would seem to not be an issue???????
 
It's one thing for the chain to move due to the tension of the valve springs. But if it's "slack," as in the chain is not tight, that's a problem. At the very least, that would be different from my bike after the rebuild (which was successful.)
 
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