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Clutch niose?

Submitted by jon_imms on Thu, 12/08/2021
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Commando

I have a 74 Commando, rode it a few days ago and noticed a noise coming from the clutch area when idling at the traffic lights. Hard to describe the noise, kind of a grumble. I'm wondering if it might be a bearing, the bike runs fine and there's no noise when moving (revs increase). I've pulled the primary cover off and nothing looks amiss, the clutch works fine and there was no change to the noise when pulling in the clutch lever. Any thoughts gratefully accepted.

Submitted by stan_thomas on Fri, 13/08/2021

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Probably the mainshaft nut has come loose. Whip off the clutch spring and tighten. Or maybe it's the crankshaft nut. Is the primary chain adjusted and aligned correctly with gearbox studs fully tight?

When the clutch is engaged the release bearing isn't doing anything so unlikely to be that. If the mainshaft nut is loose the clutch can rattle around one the splines. If the crank nut is loose the alternator can rattle around and maybe kiss the stator.

Submitted by jon_imms on Fri, 13/08/2021

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Thanks Stan, I think you may be right,  I've just been looking at it and there is some movement with the clutch basket on the shaft. My manual shows a tool to compress the spring ate so I'll need to get one of those to take the plate off.

Submitted by peter_denham on Fri, 13/08/2021

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If possible run with the case off .No harm done short term.

Submitted by ashley_cutler1 on Fri, 13/08/2021

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Sounds like a main bearing is shot, don't ask me how I know, ask my opposite number. His bearing had bad pitting across a tide line where the bike had been left standing and the nasty stuff sat on top of the oil and attacked the bearing. 

Submitted by jon_imms on Fri, 13/08/2021

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I ran it with the cover off and the noise is definately coming from the clutch area. If I take the adjuster nut etc off can I get to the nut without having to dismantle the clutch (requiring the tool).

Submitted by john_holmes on Sat, 14/08/2021

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No, any attempt to disassemble the clutch without the tool is life threatening.

Submitted by jan_nelder on Sat, 14/08/2021

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you can take the adjuster nut off, but pretty sure hole is way too small for access. Tool is not expensive, and IS needed for more dismantling.

Submitted by jon_imms on Fri, 20/08/2021

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The tool arrived and I've tightened the nut, it was loose, took several turns to tourque it. I ran it with the cover off again and the noise is still there. It's almost a sucking noise (I know that sounds weird). There was no movement in the bearing and it seemed to run smoothly. Beginning to wonder if I'm worrying about nothing.

Submitted by dave_taylor on Sat, 21/08/2021

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Perhaps the circlip behind the clutch has popped off and the basket is catching/rubbing the inner chain case?

Submitted by stan_thomas on Sun, 22/08/2021

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That circlip behind the clutch has failed for me in the past. Probably re-used too many times :). But the mainshaft nut coming loose is common enough with just the locking tab used, again often re-used too many times, or just the spring washer on the earlier bikes. Worth putting some loctite on the mainshaft threads.

 

And, if you can't eliminate the noise you should check out Ashley's suggestion about the mains. Using a long socket extension bar placed to your ear, touch the other end to the gearbox and crankcases to narow down the location of the noise. Probably best to put the primary cover on while you do this. A stethoscope is even better if you can lay your hands on one.

 


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