Timing chain

Oh, another question for you. How far should the timing chain tensioner be out? When checking valves over weekend I noticed that the tensioner is out by about 2/3 travel. The cam sprockers seem fine, could not see any obvious wear. Thanks again for your time and help.

Is there anything in the service manual about this? I don't have the manual with me here at work and I don't seem to recall reading about this....other than how to reinstall the tensioner after shimming the valves. I would imagine that there should be some amount of movement on the tensioner even when the engine is brand new. Someone, whose opinion I respect, told me that he replaces his cam chain once a year. If it's not too hard to replace the chain, I suppose that it would be good insurance to do so. HLSM lists the chain at $45.

Boit, the manual is sketchy on this. It says that both the chain and sprokets should be replaced as a set but I find this out of reach. I would venture that replacing the chain only should suffice. I was considering all this but was concerned about both installation and cost. I looked over the manual last night and it seems it can be done by simply removing the magneto and going in through there. 45.00 US sounds good also. I will have Alary up here in St-Jerome quote it CDN but will probably end up cheaper to have it sent up UPS. Am I right about going in by the CDI opening and what do you think of chain only?


You are right, the way to replace the chain is by removing the flywheel, rear chain guide, and tensioner, cams, etc. Not a very involved job, but you will need a flywheel puller.

I have also wondered about chain stretch, the manual doesn’t address this, and I’ve also heard that some replace the cam chain when they do the top end, for example.

I also agree that it doesn’t seem reasonable to replace the cam gears with the chain. The crank gear has fewer teeth, and so would be conceivably be subjected to more wear, and to replace that you need to get another crank.

How many hours are on your bike? Not sure about mine, I’d guess at least 140 or more, same cam chain. I’ve never heard of anybody having one break (unless something else broke first), but that would be disastrous.

Besides what you mentioned above is there any other reason you are wanting to replace yours?

[This message has been edited by Hick (edited 05-28-2001).]

I had an interesting thing happen to my 98 400. I bought it used and raced it 3 times. In the 3rd race the motor started knocking terribly. I took it to the shop and the yamaha mechanics couldn't figure out what it was. On teardown, the valves were hitting the top of the piston. I believe it was the intake valves because three on one side was hitting. They wanted to replace the intake cam because they thought the sprocket spun on the cam. Too expensive to just be guessing at things. I just told them to replace the chain for starters and see how it went. It fixed it and I have about 10 rides since then. I did have a cb gear key go south since then, but it was an easy fix. So, just from my standpoint, Replacing the chain may not be a bad idea. Cheap also.

I agree with Hick. Changing cam sprockets seems like asking for trouble since they are press-fit items. I would be surprised to see excessive wear at the bottom sprocket due to the constant oil bath, but it's certainly possible. You could make that determintaion once you get the flywheel off and go from there.

Thanks for the great feedback guys!

Hick, the reason for my worry is that the tensioner is out by 2/3 if not more. That indicates possible chain stretch. I bought used and got taken due to my not being around bikes for 20 years. The bike was thrashed. I did top end, links, suspension.

Boit, would you have a phone or web / e-mail for HSLM ?

Fourbanger, your senario is what I am worried about. Glad it worked out for you with no damage.

Will replace chain mid summer when I do the valve shims.

Thangs again for your time and help.

[This message has been edited by Hugh LePage (edited 05-29-2001).]


I see they've added some stuff to this site. It should be really helpful when you just want to look at the micro fiche.

Thanks Boit. I'll look into it tonight after work.

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