Cam chain guides

Long time no post! After moving back to Texas, a lot of things have gone sideways and upside down, but I have not disappeared.
Question is, I was looking around a little last week and seen that the front cam chain guide is not listed at Mike's XS anymore, and I know NOS can be hard to find. Just wondering what the current go-to is for this. MIne is shedding the side rails down into the case. Thanks for helpful replies.

Mikes still has them.

Welcome back. It seems you've missed all the recent front cam chain guide developments. Yamaha stopped making them and the quality control on some of the recent Mike's offerings has been lacking. It seems many have the mounting holes drilled at an incorrect angle. But we don't have too many options here, they're the only game in town at the moment. We may have come up with a substitute solution though, adapting an SR500 guide. See Jim's thread on the mod here .....

http://www.xs650.com/threads/cam-chain-guide-mod.51730/

This should work well but no long term testing has happened yet.

5twins said:

This should work well but no long term testing has happened yet.

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I also modded one for @MaxPete So, between his and mine, we should start putting some miles on 'em next year.

I've gathered up some of my old ones from past rebuilds and parts motors (5 so far) in anticipation of making some of these. I have an interesting observation. All appear to be originals that I assume were factory installed, and 4 out of the 5 show rub/wear marks along the sides, into the lip of the channel. This would indicate to me that Yamaha didn't even bother centering these things when they assembled these motors, lol.

5twins said:

This would indicate to me that Yamaha didn't even bother centering these things when they assembled these motors, lol.

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I wonder.... if a chain doesn't get adjust for far too long, if there's and side to side vibration thing going on....

Well, maybe, but the wear marks on these are at the top and/or bottom only, none at the middle sides. That would seem to indicate they were mounted crooked. I'm going to get some pics before I sand them down flat.

5twins said:

the wear marks on these are at the top and/or bottom only

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Yeah... that would tend to rule out a lateral vibration.

JimD54 said:

I also modded one for @MaxPete So, between his and mine, we should start putting some miles on 'em next year.

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Indeed - and Jim did an excellent job on the “Frankenguide” which consists of a stock guide rubber and metal backing plate from a Yamaha SR500 single bolted with special aviation high strength fasteners to a bare XS650 metal “shoe”.

I like the stock SR500 guide which has a raised central “rail” rather than the raised side rails that are on the XS650 variant. That raised central rail will ride on the nice smooth chain rollers and in my view, is much less likely to be chewed up by the sharp edges of the side plates of the timing chain which is one of the common failure modes of the XS650 timing chain guide.

As 5Twins points out, the other key issue is centring the guide within the cavity between the cylinders so that the chain doesn’t scrub against the side rails of the stock XS650 guide. There isn’t much clearance in the guide mounting arrangement - but there’s no doubt that it could be significantly misaligned if it were not installed carefully.

Subject to Jim’s and my testing, I would suggest that Jim could have a great little business doing these mods on other folks timing chain guides. That would address what seems to have emerged as one the very few weak points in the XS650 powertrain. He does excellent work and it sure looks like a winner to me!

Pete

I don't have all the tooling that Jim does but a buddy has a disc sander I can use to sand down the old guides. I'm pretty sure I can handle the rest with the tools I do have. I've already made a nice little angle "holder" to bolt the guide to and help hold it nice and square to the sander table.

5twins said:

I've already made a nice little angle "holder" to bolt the guide to and help hold it nice and square to the sander table.

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If you wouldn't mind... maybe add a pic of that to the 'mod' thread? Might help someone else who wants to try it.

Don't need a countersink.....Pre-drill a pilot hole with a very small bit. Then use a large drill bit, as, and the size of the countersink that would be needed and just go the depth needed, (use the drill on a fast speed and light application so it doesn't grab). then drill the correct size hole needed......

Countersink tooling isn't very expensive. Although it is difficult to find in anything but SAE sizes. Standard aircraft hardware uses a 100 degree countersink angle, so if you used a 90 degree or 135 degree drill bit to countersink, it would end up stressed at the top or bottom of the hole, depending on the bit angle used, and would not develop good bearing strength. Pan American Tool sells most types of countersink tools available. I considered at one time looking into the chain guide stock available and working out a "re-sole" procedure on them. I found McMaster-Carr and a couple other industrial suppliers carry the extruded 6-6 nylon and other materials in standard chain sizes. Thanks for the update. Gonna check out that mod thread now.

The problem I see with nylon, teflon, and the like is what comes off it as it wears, and were does it go?

well, the current material ends up in the screen and filter, I know that. LOL