Rear chain chatter

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Jul 10, 2007
73 850. Im getting some chain chatter on the rear chain where its slightly rubbing the inside of the rear of the primary on the left of the case on the return or bottom side. Its very very slight but noticeable when rolling the bike before starting it etc. The thing tracks straight hands off bars. Do I have a sprocket problem or something? Not my bike but a resto for a friend. Thanks, Dave
I'm afraid the primary chaincase is out of alignment. You will need to strip the primary and check that the bolts securing the inner chaincase to the crankcase are tight, then look at the center mounting stud for the chaincase. There should be enough shims on the stud that there is no play between the inner chaincase and the stud. Now turn the rear wheel and observe the chain. If it is still rubbing the inner cover, then you may have a chain with side plates that are too thick. Most standard 530 non-o-ring chains (Renold, DID, etc.) will work, but #50 industrial chain will fit the sprockets, but are often too thick. If you have eliminated this possibility, then check you engine mount bolts. These often loosen and can wear the holes in the crankcase oval or even fracture. This could possibly allow the engine to shift slightly in the mounts and cause mis-alignment of the chaincase.
Had this problem too... wore a groove into the back of the inside primary cover. As said, some chains too thick, but as also said, I think might be missing shim. Suggest loosening the center primary nut, and if noise goes away, the primary case is indeed most likely misaligned or the shim is missing.

Just a trick, if after checking the three mounting to motor block bolts inside the case, those motor mount bolts mentioned above and such...loosen the stud nut a good amount, check with a mirror and a flashlight if a free space appears back there between the stud and the case back then get a couple different thickness washers of the right size, and cut a slot, make it into a "U" so then you can , lightly pry the case out a bit and fit the "U" down over the stud between the case and the stud and snug the stud nut back up and see if that works. A bit of delicacy and you will get the case aligned and the rubbing chain noise gone without having to remove the inside primary case at all... :wink:

If there appears then instead, another aware that inside the case, where the clutch center fits onto the tranny shaft, there is a thin ring that holds the center in it's proper position, and that can be bend by over tightening the clutch center nut. That noise can therefore also be inside the case and be the clutch center and not the final drive chain...that is if anything seems take the advise and take the stuff apart and look...don't go for a weekend away and expect the noise to just go away by itself... :(
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