Front sprocket wearing strangely...
 

Im in Tanzania at the moment and about 1000km ago i checked my front sprocket. Firstly its wearing quite badly in the usual sense, that is the teeth on one side are wearing. Though this is understandable what concerns me is the wear Ive noticed on the engine side of the sprocket.. Its as though the chain is wearing away at the thickness of the sprocket on that side. The rear sprocket and chain seem fine.
I have a new set, but also a long way to go so Ive flipped my front, with washers under lock plate to make up for raised lip.
Any ideas or comments?
Jim
PS so far done about 9000km on this set.

Have you had a good look at the chain alignment?

Looking from the rear, you may see that the chain is misaligned. Could be simple wheel misalignment, in which case make sure the wheels are in alignment and the chain should follow. DO NOT trust the chain adjuster marks. See article in HU Tech section on chain alignment for lots of details.

Finally, could be bent frame/swingarm, in which case live with it for now as long as the bike rides ok otherwise. DO check for cracks in the frame / swingarm.

Turning the front over is a good fix for now, but you need to find out why it's happening.

------------------
Grant Johnson

Seek, and ye shall find.
------------------------

One world, Two wheels.
www.HorizonsUnlimited.com

Last thought - re raised lip - sure you had the sprocket right way round to start with? http://www.horizonsunlimited.com/ubb/wink.gif

I used to have the same problem. I always use original Yamaha sprocket which has a separate spacer ring on the engine side, contrary to the imitation ones which come with a flange spacer fixed to the sprocket. Sizes [read : width] are not always the same. So I started mounting thin additional spacer rings to position the sprocket away from the engine, which solved the problem. And yes, I always trust the chain adjuster markings on the swingarm, after once having measured the straight position of both wheels compared to each other.

------------------
Fred, XTZ660, Holland.

My two cents: I have this on my Tenere and a freidn of mine also on his. Absolutely no worries for this bike. Chains still last very long.

Auke

Maybe, but this situation definitely eats the front sprocket, so do something about it like I did.

p.s. not only because in principle I disagree with my friend Auke!

------------------
Fred, XTZ660, Holland.

Thanks for all the Info!
Ive checked everything i can think of and it remains a mystery. I guess i will have to live with it...

Firstly, sorry for jumping in on this so long after it was initially posted, but I have just changed the front sprocket on my 1999 XTZ660 from a 15T to a 16T to try and drop the cruising revs, and noticed something unusual with my CS sprocket setup.

The locking plate for the nut on the countershaft was not engaging with the splines on the shaft, which basically rendered it useless. This concerned me a little as I purchased the bike second hand and the plate appeared to have been 're-used' more than a couple of times. Since buying the bike, I have done about 5000km and it has not been a problem at all (it was still attached to the bike!)

On removing the sprocket, I noticed the reason for it. There was a spacer about 4.3mm thick between the sprocket and the oil-seal cover which I was not able to find on my spare-parts CD. (Having said that, my CD is for the earlier 1996 model XTZ660.) This spacer had the effect of moving the sprocket further away from the crankcase and subsequently not allowing enough of the splines to engage with the locking plate. I was searching for why my bike would have this spacer when I came across this thread. The spacer appears to be a factory addition, it has machined grooves for the splines...perhaps they recognized this alignment problem and corrected it on the later model bikes? Anyway, no problems with abnormal wear on the sprocket, but no security locking washer for CS sprocket.

Hope this sheds some more light on the subject. If anyone has an alternative for securing the sprocket without the washer I'd be keen to hear about it. Otherwise it is going to be lotsa Loctite.

The spacer serves with a different (narrower) sprocket.
Many aftermarket sprockets replace the washer like the wide previous model sprockets did.
You have to use the washer to secure the nut. Loctite does not do the job.
I saw the problem last friday on a 2002 XT600. He lost his nut somewhere in the bundo the previous weekend leaving him stranded.

Lost nut
 

I once lost the retaining nut on the countershaft of a 550. I used a peice of strap metal clamped to the frame with hose clamps. I then bent the metal to press against the outside of the countershaft and keep it pressed in on the shaft so I didn't loose too much oil. On my bike I lost the use of the clutch but I made it to someplace where I could get another nut.