Cam Chain

[Hepcat]

I know when you adjust the cam chain tensioner, you're supposed to turn the engine clockwise, and only clockwise. My question is...Why? I don't think I've ever heard anyone explain it. I know it results in improper tensioning, but what causes this?

I was just thinking about this on the ride to work and it's bugging me. I figure it has to do with one side of the chain having tension caused by the drive sprocket pulling on it and the other side having more slack (Like pushing a rope, it just doesn't work). Is that what it is? Is the tensioner on the side that's slack, so when you turn it backwards it's not taking up slack, but being pushed out by the chain? can you damage the engine by turning it backwards?

Thanks!

[sidecarKev]

I think you hit on it. If you turn it backwards the part of the chain that is usually slack is now tight. So you would be adjusting the tensioner on the tight part. Now when you go to start it up your chain could be really loose and could skip a tooth or two. Then ya got trouble.

[John]

Jon, the engine turns in a ccw direction, so the front side of the chain will be the slack side, and there fore that is where the tensioner is. If you should turn the engine backwards, then in theory the chain could jump a tooth, and things would be out of time.

[rover]

Topic Review (Newest First)


John Jon, the engine turns in a ccw direction, so the front side of the chain will be the slack side, and there fore that is where the tensioner is. If you should turn the engine backwards, then in theory the chain could jump a tooth, and things would be out of time.


And valves would hit pistons, resulting in XSive damage. Word of caution, DO NOT ROTATE ENGINE COUNTER CLOCKWISE

[John]

Rover, you are so right. I don't know what the hell I was thinking. I know better than that, really, I do. I guess pain medication, and a cold one really don't mix.
Hey kid, sorry 'bout that. I hope you didn't get to read it yet.

[Hepcat]

Thanks again guys,

I just couldn't quite wrap my mind around it while riding the bike...once I sat down to type it up, I guess I figured it out pretty closely, I was a little suspicious about the valves too...

[prometheus578]

If you crank the engine backwards... for a few moments as the crank takes up the slack from the chain on the front side of the engine, the pistons are moving, but the cam and the valves are not. I... um... errr... guess that's how I bent an exhaust valve once. (and I didn't crank it back far, either)

[Dennyz]

The valve to piston clearence is such that if the timing chain is loose and everyting is in the right place, turning the engine the wrong way can bend a valve, and it does not take much effort.

[skids]

That would obviously mean that one should first do a cam chain adjustment prior to adjusting valves. I say this because when using the valve tool, it requires that the cams be turned the wrong direction when the exhaust shims are to be removed. Right? This always makes me nervous!

Originally posted by Dennyz
The valve to piston clearence is such that if the timing chain is loose and everyting is in the right place, turning the engine the wrong way can bend a valve, and it does not take much effort.