Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: adriangsmith on August 21, 2017, 04:13:03 PM
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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??
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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.
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You didn't buy some extra wide X ring chain did you?
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X-ring still fits okay (just).
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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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Well spotted.
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The f2 sprocket fitting is different to the k models. Sprocket probably wrong way round.
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Thanks all, I'll check that tonight and get back to you all.
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You were right Royhall, had the sprocket round the wrong way, chain has worn a small groove in the lower engine cases but should be OK still.
Also have seen some rubbing on the sprocket engine cover.
Hoping all will be OK otherwise i'll be switching back to the the 530 chain setup.
Out of interest does the chain retaining bolt have a special washer? Mine just has a m8 penny washer on it and the sprocket still has some movement in it is this correct?
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That is not correct, there should be the penny washer then a spring washer....... Good your sorted, glad I could be of assistance for once....... Got the T-shirt myself for that one.
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Out of interest how did you retain the F1 engine sprocket as they have the splined tab with 2 bolts in the groove machined into the output shaft?
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Out of interest how did you retain the F1 engine sprocket as they have the splined tab with 2 bolts in the groove machined into the output shaft?
It was secured in the same way as the f2 one witj a penny washer on the end of the shaft.
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