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Sprocket wear

ichabodnt650

AAA maps and DSLR
Joined
Feb 5, 2004
Location
Mountain View
Moto(s)
KTM 690 SMC, Piaggio Liberty
Name
Ich
I pulled my wheel off for a tire change today and saw some weird wear pattern and damage. Never seen this before. Any idea what went wrong?

KTM 690 SMC, this sprocket replaced the worn OEM at 17,000 miles. It is now 9,500 miles later.

520 chain and sprockets, same 16:42 as OEM when replaced.

This was the sprocket I bought and installed. Is this "lightweight" sprocket weaker than average? Are they race only? Light but faster wear?
https://www.amazon.com/dp/B08F6K156R

Could I have kicked up some gravel that chipped a tooth and the broken tooth strained adjacent teeth until the failure propagated like a zipper?

Are big cc thumpers normally harder on drivetrain than inline-4 or flat-6 motors?

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Front wear pattern
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That’s crazy wear! So did you change front sprocket and chain at same time you changed rear sprocket? At first I thought these were aluminum sprockets but even your link shows steel sprocket. If there’s no Cush drive in the drive train and your accelerating, compression breaking I could imagine the wear occurring faster than normal. Chain looks very clean.
 
... did you change front sprocket and chain at same time you changed rear sprocket?
All 3 were changed together.

... no Cush drive in the drive train and your accelerating, compression breaking I could imagine the wear occurring faster than normal
The rear does have cush drive blocks.

Chain looks very clean
I use diesel and a paint brush every 300 miles or so to clean the chain. It removes sand, dirt, or any grit from tearing the O-rings. No lube, only the sealed roller grease behind the O-rings need lubrication.
 
It looks like the remaining teeth have cracks at the base of most of them. Also, the missing teeth look like they broke off at the same angle that the cracks are showing on the remaining teeth.
Why?
I have no idea. I have never seen this kind of wear before.
 
:wtf With missing teeth in the rear sprocket like that, shouldn't you have felt the chain slipping badly for a while?

I replaced chain/sprockets on my '07 690SM at 23k mi, so that's no worse than a typical multi-cylinder bikes. The drive train felt a little loose (i.e., chain lash) at that point, and the teeth of the rear sprocket looked pointy, but nothing crazy like that. I clean w/ WD-40 sprayed on a rag, and lube with Dupont chain-saver (wax based) at 600-800 mi intervals.
 
Sprocket wear that I’m accustomed to is different from what you have. I think the sprocket is defective/ maybe overly hardened., the wear i’m accustomed to is ~the back side of the tooth wears forward( gets thinner and then the teeth will break.
From your picture, it doesn’t look like the backside of the tooth is worn that much. Your sprocket tooth breaks like it’s brittle/it’s overly hardened.
I’m gonna call that sprocket a factory defect.
 
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Is the master link a 520?
According to wear...you compression brake hard and alot.
 
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this picture looks like you don't really lube/clean your chain frequently. this will accelerate wear on the teeth of the sprockets as well as giving you those stiff links like at approximately 1'oclock in the picture.
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the rollers are lubed inside yes. without lube on the roller/sprocket interface it's metal on metal contact and the side plates need a little love to keep them rotating nicely about the pins

Are big cc thumpers normally harder on drivetrain than inline-4 or flat-6 motors?
i'd expect so. 1 big power pulse vs several smaller ones
 
this picture looks like you don't really lube/clean your chain frequently. this will accelerate wear on the teeth of the sprockets as well as giving you those stiff links like at approximately 1'oclock in the picture.
attachment.php

the rollers are lubed inside yes. without lube on the roller/sprocket interface it's metal on metal contact and the side plates need a little love to keep them rotating nicely about the pins

Are big cc thumpers normally harder on drivetrain than inline-4 or flat-6 motors?
i'd expect so. 1 big power pulse vs several smaller ones
 
Next set might consider a 525 or 530. Just because.

My puny SV650 is still running the stock 525.
 
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IMO, that metallurgy is suspect. I've never heard anything great about JT and this supports that. Send a email to the manufacturer if you care enough. Maybe you'll get a free set of sprockets... if you'd actually use them after this.
 
Is the master link a 520?
Yes, it is. Rivet 520 master link that came with the 520 chain.

...you compression brake hard and alot.
Good eye :thumbup Yes, I do

... stiff links like at approximately 1'oclock in the picture
That link isn't stuck as the picture suggests, nor are any of the other 113 links :teeth (it was hung up out of the way in the photo to show the countershaft sprocket teeth)
 
I'm ordering another Jomthai sprocket, this time their regular steel instead of their lightweight steel.

https://www.amazon.com/dp/B001AVS7GC

I've run multiple JT sprockets on ZRX1200, DL1000, FZ07 in the past without issue, but those were their wider and stronger 525 or 530 (and they were not lightweight steel).

I'm suspecting this lightweight and narrower 520 may not be beefy enough for longevity on a 693cc thumper :thumbdown
 
I'm ordering another Jomthai sprocket, this time their regular steel instead of their lightweight steel.

https://www.amazon.com/dp/B001AVS7GC

I've run multiple JT sprockets on ZRX1200, DL1000, FZ07 in the past without issue, but those were their wider and stronger 525 or 530 (and they were not lightweight steel).

I'm suspecting this lightweight and narrower 520 may not be beefy enough for longevity on a 693cc thumper :thumbdown

I would order a new countershaft sprocket and chain also. I wouldn't run a new sprocket on that chain.
 
Sprocket wear that I’m accustomed to is different from what you have. I think the sprocket is defective/ maybe overly hardened., the wear i’m accustomed to is ~the back side of the tooth wears forward( gets thinner and then the teeth will break.
From your picture, it doesn’t look like the backside of the tooth is worn that much. Your sprocket tooth breaks like it’s brittle/it’s overly hardened.
I’m gonna call that sprocket a factory defect.

This. It’s a material thing. Could be just about anything, but I’d contact the manufacturer and complain.
 
I've never seen anything like this. It's clear the sprocket is cracking due to poor quality. I would dump both sprockets and the chain and start over.

Your drive system is more important than some understand. If it fails you can do major case and swingarm damage at best and or lock the rear wheel and sent you bouncing down the road.
 
I just noticed that you cheaped out. As nd bought it for 27 dollars on Smazon. Next time spend the money for a brand with a good reputation.
 
I just noticed that you cheaped out and bought it for 27 dollars on Amazon. Next time spend the money for a brand with a good reputation.
 
My $.02- this is not a place to experiment with lightweight or cheap components on a street bike. Not only is the weight difference practically immeasurable in performance, that chain jumping and sticking between the swingarm and sprocket could cost you everything. You got away with it once, just buy a quality brand next time.
 
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