Drive Sprocket Question

My chain was eating the chain casing. I dismantled everything and have what is probably a pretty stupid question. Which way round does the drive sprocket go? It is cupped. If it were a saucer with a tea cup, does the tea cup sit on the saucer toward the transmission or toward the clutch? I had it toward the clutch which, I now understand, is probably reversed. Your help much appreciated, at the risk of showing what a dummy I am!

TRANNY SIDE


CLUTCH SIDE


Also, fwiw, the big left threaded nut has chamfers around the outside corners that go to the gear side or the nut will not fit flush.
A common mistake.

My Banker-humanoid said no question is too dumb. I liked the reply so much I gave her my money. Yes, the chamferred- bevelled side of the big nut goes against the cupped side (facing outwards) of your sprocket (which still looks acceptable). The reason being the angled slope and full contact with it.

Quebec Bob said:

My chain was eating the chain casing.

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It appears the sprocket is fitted correctly so Is the chain an 'O' or 'X' ring type, as they are wider than standard 530 (5/8 x 3/8) chain?

If your drive chain is eating up your chaincase (inner primary) then you may need an other shim on the central post.

Item 11
http://www.oldbritts.com/1972_g8.html

Could also be the chain case is incorrectly shimmed against the middle pillar bolt/ stud.

pvisseriii said:

If your drive chain is eating up your chaincase (inner primary) then you may need an other shim on the central post.

Item 11
http://www.oldbritts.com/1972_g8.html

Click to expand...

This is a fairly common issue - people don't realize how critical the proper shimming on this post is. Problem is it requires removal of the primary inner case to correct. Since you've got a drive sprocket in your hand, you probably have the primary inner case off. Once removed, check that the inner primary isn't bent by placing it open side down on a flat surface. Once satisfied its flat, offer it up against the crank case, and make sure its laying flat against the milled face of the case. now you can measure how much shimming you need on that central post to ensure flat mounting on the crank case and clear passage of the chain at the rear of the primary. Install the shim or shims, mount the inner primary, and verify everything's good.


An O-ring 530 chain will not fit without grinding against something. There is a 520 O-ring conversion available, which requires machining the rear sprocket and getting a 520-compatible front sprocket.

So I did have the sprocket on correctly and thought I had carefully shimmed everything but I'll check it all again on the weekend when I receive the new sprockets ordered for front and back as the misalignment of them ruined them. So there's another clue. I'll-check the rear hub alignment when I reassemble everything as well as the width of the chain. I really thought everything was running straight but it appears it wasn't. Thanks for the help.

Other thing you might check is the thick washer on the gearbox top stud should be on the drive side, inside the cradle next to the gearbox. Sometimes these get left out and then things aren't straight. You may want to check the clearance between the swing arm pivot and the primary inner cover for clearance, it's not much, but about 1/8" or so, certainly not touching. Any of the previous things can be out of whack, but for sure I'd check the shims on the center primary stud from the cradle and make sure your inner cover is straight with the engine crank drive side face and not warped or bent. Since you've got the inner cover off, you can check all these things out.

Dave
69S