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new chain and sprocket vibes

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adriangsmith:
Hi All,
Recently changed the chain and sprocket on my CB750F1 / F2 mongrel (F2 engine and wheels).
Ran nice and smoth no vibrations before but had the F1 530 chain and sprocket setup with an 17 / 40 (8 tooth undersize) rear sprocket combo.
Changed up to the F2 spec 630 chain and sprocket 15 / 41 tooth combo and now have vibrations at 4,500 - 6500 rpm.
Any ideas??

royhall:
Did you make sure that the front sprocket is on the right way round (raised part inwards). If it's the wrong way round the chain will cut into the crank case. The 630 chain clears by about 1mm so its essential. What you describe does sound like the chain hitting the cases.

mike the bike:
You didn't buy some extra wide X ring chain did you?

royhall:
X-ring still fits okay (just).

MrDavo:
I fitted an x ring chain and was aware that something was fouling, I could hear and feel a 'ticking' that was related to road speed rather than revs.

Turns out that despite the nuts being held captive by a locking plate, the sprocket studs were unscrewing from the hub, and starting to get their ends machined by the swinging arm every turn. It was hidden away on on the mside, machiniing a permanent litlle notch.

I found it while cleaning, just before setting off for Crich, when I found, to my horror, that two of the bolts were loose, with nuts still on, where they should be, in their locking plates. The bolts were unscrewing themselves out of the nuts, once they had become loose in the hub thread. it was the loose washers I spotted first, as I wiped the clag off them - then I saw the machined stud ends.

I'd never really checked the tightness of the sprocket nuts before, as it means flattening all the lock tabs first, then putting them back afterwards. You assume that if the tabs are intact, then all is well.

One to watch for.

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