Cam chain replacement

[James England]

Hi everyone. I have another few questions for the combined brains of the forum.... cam chain stuff this time. All responses gratefully received...

How long does a camchain last? Mine has done 43,000 miles and I'm thinking of replacing it as a precautionary measure. It's not doing anything untoward but I wonder what the service interval is....

Do camchains usually have a joining link? I'm assuming so but am not sure. If they do, how does one secure the joining link rivet into place to avoid any castastrophes like it coming loose?

What tricks do you know about how to replace the camchain? Anything to watch out for especially?

Finally..... what make of chain would people recommend? I'd like the best there is......

Thanks!

[DGXSER]

James, As to when to replace, I would look at your tensioner. Pull it out without loosenign the adjustment and see how much room is left on it, that will let you know how stretched the old one is. But at 43k, I'd go ahead and do it during your next planned maintenance down time.

They have master link in them. It takes a specific tool to remove them and to insert them. I've not done one yet myself, but have witnessed it a couple times now.

[bikerphil]

Cam chain from Z1 recommended by fellow member....

http://www.xs11.com/forum/showthread...ight=cam+chain

[3Phase]

Check the camshaft timing

James, it might be a good idea to replace the chain by miles traveled just to be safe but you should check the camshaft timing before you buy a new chain. The cam chain might be okay, it might be worn or it might have already been replaced with a new chain. Measuring the tensioner travel alone doesn't really give you a good picture of what's happening to the camshaft timing so you should check the timing marks on the camshafts.

When you turn the crankshaft to TDC for the #1 cylinder ignition stroke the dots on the camshafts should align exactly with the arrows on their respective bearing caps next to the camshaft gears. As the cam chain (and to a lesser extent the gears) begin to wear out, the exhaust camshaft will lag further and further behind he intake camshaft and retard the exhaust camshaft timing. It will happen even if you keep the cam chain tensioner adjusted.

For an extreme example, here's a picture of the camshafts in my '79 Special with 123,000 miles on the odometer. The camshaft timing marks show a worn cam chain.

[SFSPECBIKER79]

good to know

nice post scott, as shown in pic the chain has stretched a 1/16th inch or so, thanks for the pointers on the subject, i keep this in mind when i set my valves next time, i didnt know they should be perfectly alligned with the markers.

[3Phase]

Yes, checking valve clearance is a good time to check for chain stretch. I'm not thrilled by the idea of changing the chain but at least I know it's time to do it before it snaps.

[skids]

The funny thing about the marks is that even a brand new cam chain may not line-up exactly...at least that has been my experience.

[3Phase]

Skids, unless it's off by just a fraction of a fine redheaded frog hair that would be the time to bust out ye olde degree wheel, piston stop and dial indicator to see what's really going on in the engine.

Checking timing with a degree wheel is a little more involved than going by the dots and arrows but it will let you know if it's a just simple mismatch or a genuine problem.

Not being the innately trusting type with thirty-year-old engine parts and their associated factory timing marks I checked my '80G when I did some engine work a couple of year ago so I know for a fact they're correct on that engine. I'll do the same for the '79SF after I change the cam chain. Oh, joy!

[TADracer]

I find the dots and arrows are not the most accurate things. Think about it, they are an arrow cast into an aluminum part and a hole drilled into a steel part made on different machines and probably in different places, long before CAD/CAM and CNC machining and never being matched to each other for accuracy. They are only meant to give the alignment reference during assembly but are not meant for checking anything other than having the cam sprockets set in the proper tooth on the chain.

I have checked these things on my motor before with a degree wheel and dial indicator and both cams were dead nuts on 101 degrees lobe center but the holes and arrows did not line up exactly. Personally, I hesitate to rely on the factory marks to make a decision on replacing a cam chain, especially an OEM type that will require cracking the cases.

[DGXSER]

There is no reason to crack the cases even with an OEM chain.

[3Phase]

James, I'd still check the timing marks before buying or installing a new cam chain. Timing chains and gears are supposed to be changed as a set just like final drive chains and gears and for exactly the same reasons. Unfortunately, a lot of XS parts are discontinued or just insanely XSpensive and Yamaha doesn't even list a complete timing set.

If the timing marks don't line up where they're supposed line up there is something wrong fullstop. I have found timing gears on other engines with their timing marks 180* out but not offset one way or the other except for some adjustable aftermarket parts that are supposed to be installed and timed by the customer. Normally I wouldn't even turn the crankshaft on an engine if the marks didn't line up after replacing a timing set but the XS seems to be an exception to that rule, which is odd but it is possible that an enraged chimpanzee was tethered somewhere in the same room as the new bikes with engines spec'd so closely that a variance of one ten-thousandth of an inch is a sloppy fit. There is more to follow on the conception of the immaculate specification and mundane reality.

Yes, before I dove into the engine in my '80G I read about other members here that had timing marks that were... not quite right -- the timing marks, not the members! I figured that if the marks can be off in one direction but still in time they can be just as far off in another direction and the marks would appear to be correct but the camshafts would be out of time. The timing marks in the engine of my '80G were pretty close before I changed the cam chain but the exhaust cam was starting to lag; not as extreme as the picture shows my '79 but still lagging. The timing marks lined up exactly where they were supposed to line up with a new Yamaha cam chain; degree wheel and a dial indicator agreed with the timing marks and the camshaft lobes were all within spec for duration and lift.

The intermittent alignment problems that have been described could be mismarked or mismatched parts; cam/crankshaft gear wear; replacement cam chain with link spacing that is close to but not quite the same as the original chain.

It could also be that some camshaft bearing saddles and caps in the cylinder heads were bored slightly off center at the factory. For example: the used crankshaft I bought from a low-mileage '81 Midnight Special engine was in perfect condition except that all of the balance holes in the counterweights were drilled off-center by one of Yamaha's tethered spanner monkeys, partially exposing the outer edge of every hole all the way down one side of every counterweight. That is why I checked the camshaft timing and every other specification on my engine even though everything appeared to line up by the book. Most engines should be fine because the chimpanzee appears to have been allowed on the premises only on alternate Tuesdays and a couple of weekend graveyard shifts to reduce the cost of overtime for skilled labor.

Splitting engine cases to change the cam chain is not really necessary. Aftermarket cam chains use a master link and even Yamaha itself now appears to have a mixed parts stream. The new cam chain I bought from the dealership, bagged and tagged with Yamaha prices and part numbers, came with a master link just like the aftermarket cam chains. I had one of the highly-tethered technicians at the dealership install the link for me as I already had the engine apart at the time but I didn't have a cam chain tool. The new cam chain has worked for over thirty-thousand miles now and the camshaft timing marks are still exactly where they are supposed to be.

Happy time! (Ding!)

[James England]

Thank 'ee 3Phase and y'all.

I have a question... how does the master link work? I presume it's NOT like a pushbike master link with a spring clip. I'm guessing it involves some kind of rivet-squashing tool that does something to the ends of the master link, right? How does it actually do the job? Is it reasonably easy?

[bikerphil]

Yep, you use a riveting tool. It mushrooms the ends over. It can also be done the po' mans way with a center punch and hammer with a helper holding a heavy solid bar on the back side of the link as a stop. MikesXS sells a tool like the one below for less $...

http://www.amazon.com/Motion-Pro-Cha.../dp/B000HHYVD8

[3Phase]

James, Phil's got it!

If you look at the picture of the '79 cam chain you can see one link that is not the same color as the rest of the chain. That is the master link. If you click on the picture it will load a larger image with higher resolution that you can magnify so you can see how the link is attached.

[James England]

Nice one. Thanks. I think I might be able to use a small chain link riveter from my pushbike kit actually. That or the centre punch route, I guess.

I'll check the valve clearances and do the cam chain this winter. All is fine (so far) and too nice weather to take the bike of the road. A nice bit of 'work' for the winter.... in the shed, radio on, kettle on, feeler gauges and shims at the ready, rivetter by my side......