Cam chain rattle

[Tompasio]

Cam chain rattles pretty loud when engine is cold,but quiets down a lot when its hot,WHY????

[terrylee]

rattle

I'm no mechanic, but is this noise just while the bike is warming up and maybe idling low? My does that, but as soon as the rpm increase the noise stops. My noise is also not much more than a loud tick. Seems alot of GS do that at idle. terrylee

[mike_of_bbg]

Mine makes a horribly unnerving racket starting at 2500, then smooths out at 4500+. But yes, the rattle is worst when it's cold; it gets much better after it warms up. My tensioner rebuild parts should be here any day now. I should get to the rebuild this weekend, then will report back on what I find.

[Suzuki_Don]

It seems like all you guys need to do the seals, "O" rings, etc and do the cam chain tensioner rebuild. Follow Bwringer tutorial here http://bwringer.com/gs/camchaintens.html Do this and you will have no more problems. Once you give it a good clean out of the old oil, grime, etc. it's amazing what a diference it will make. If the spring loaded shaft is stuck and will not take up the slack in the chain then you will have the resultant noise. Clean it up and everything should be OK.

[Poot]

I have done the rebuild, and I still get some rattle at warm up, as well as at certain rpm's.

a lot more when I come down on hard downshifts (into the 6000rpm+ range)
.



hmm...



POOT

[mike_of_bbg]

The answer

OK, I just took apart my tensioner. The answer, at least in my case, was that the outer spring had grown tired and would no longer advance the plunger to contact the beveled end of the push rod. Here's how this works:

The push rod has a linear spring which pushes it against the chain guide. That much is obvious. The force of that spring alone, however, is inadequate to hold the chain guide against the force of the chain with the motor running.

So you see that beveled end on the inside of the push rod? As the push rod advances, the outer spring (connected to the knob you can actually touch) turns the knob and shaft clockwise, which in turn advances a plunger to press against the beveled end (the plunger has a small "ball" shape on the end so it's just a point contact). That plunger then keeps the push rod from coming back out of the motor. Except in my case, the outer spring was exhausted in its position after 30 years and would no longer advance that plunger.

Had I just put another turn of tension or so on the outside knob, it would have traveled the distance and locked the push rod in place. And I would not have felt compelled to shell out $10 in parts, and wait while Suzuki ships them in and my parts soak in Berryman's. Then again the oil seal was pretty loose and there was some wet there, so I'm probably better off. Plus I have to wait for some more parts anyway...

Best of luck to you with that. Hope that helped.

Oh, and my best guess as to why it helps to warm up the engine is that the metal parts of the tensioner expand and take up the slack. particularly the push rod, but likely also that plunger.

[Tompasio]

I turned the knob spring 1/2 turn counterclockwise,NO MORE RATTLE.

[mike_of_bbg]

Good to hear. I put the carbs back on and took mine out for a ride - no rattles here, either

Bottom line: If your cam chain rattles, walk up to your cold, non-running bike and try to turn the knob clock-wise. If you can turn it at all, you need more spring tension.