primary chain

My primary chain was clunking at idle on my fz600 (same engine as an xj600). Only really apparent at idle because there's not enough oil pressure on the tensioner.
As it's around $200 for a new one I was wondering what's the usual life on one of these chains. Have it out and it's somewhat slack, bike has 35,000km's on it. Could I get away with shimming the tensioner slightly? What's the expected life for them?

 

Good question. In application, I've yet to replace mine. Any engineering geeks out there? I suppose you could but you still would need to address the root problem (I understand it is low oil pressure, yes?). Without dealing with it first, your efforts are probably doomed to suffer yet again. I haven't a clue as to the dynamics nor construction design of your machine, so really I shouldn't say much. I understand just how very important it is to keep oil pressure up in a motor (torn too many oil starved machines apart) and feel that if your chain tensioner is suffering, what else is as well? Bearing surfaces, etc, need to pressure to survive and it just doesn't make sense to try to cheap out on giving the bike what it needs to stay healthy. Go replace the pump and be done with it! It also may be that an engineering problem existed and a revised design is in place, one never knows. Check with your dealer for the latest and greatest. Good luck to you, I hope I was of some help.

 

don't mean the bike has oil pressure issues, just that the tensioners are oil pressure driven so at idle when the pressure is a bit lower they don't press agaisnt the chain as much and this was how I could tell it was getting slack(from the noise of the chain at idle) and opened it up.

I just want to know how many km's you guys usually get on your xj600 primary chains, as mine has 35,000 and not sure if it actually needs replacing yet. (as opposed to just shimming the tensioner and maybe upping the oil pressure a little)

 

Well - I am not sure if shimming would help. I don't know your design, but lets use an example that I know:

If you shim the back of a brake caliper piston, will it cause the caliper to travel farther? No - in this case because the distance is determined by the brake rotor.
Will it cause the caliper to push harder? No - because force on the brake rotor is determined ONLY by the surface area of the back of the piston and by the fluid pressure. So, if you shim the back, you still have the same surface area, and therefore, the same force.

If your design is similar to this example, then you will not gain anything by shimming. Is it hyrdraulic only? Is some sort of spring used? Are you shimming against some metal so that it acts like a piston stop instead of a shim? That last idea would work for your case, because you just want the piston to work at idle, the lowest pressure.

ALSO - from what I have read about chains on chain driven bikes - chains begin to stretch quickly right before failure. So - I wouldn't expect failure anytime soon, but if it starts to happen at higher RPMs, then you can assume the chain is stretching and it is about to fail.

Are you absolutely sure the sound you are hearing is the chain? My manual doesn't say anything about this being a maintenance item.

 

shimming would work fine if the chain was a little stretched, it has one fixed tensioner and one oil driven one, so you could just shim the oil driven one so it starts its travel a bit farther out.
yea it was definetly the primary making the noise (quite a common thing on xj600's too), anyway took it to a mechanic that deals with a lot of xj600's and says this one's pretty far gone so I just got a new one.

 

I'm glad you figured it out.

 

I'm glad your dealing with it now instead of the aftermath of a broken chain!!!! Good call and Rich, your post was a great explaination, thanks!

 

yea, it's expensive but the engine's not going to be in parts on my workbench again
thanks for the help