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Engine sound

Currie

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Hello, first post here. Last week I picked up a 1980 cb750. Just got it running and it has a knocking sound at idle that goes away with any revs at all. I was thinking cam chain but then by advice on a fourm I put it in gear (on the centre stand) then I put the brakes on and released the clutch about half way and it seems to go away. No metal in the oil thankfully, but I still really dont like the sound. Its hard to tell where the sound is coming from exactly there's lots of sound in my small garage and lots of intake noise with he airbag still not being on. Any ideas on how to rectify this?
 
Primary chain, which is hydraulically boosted, the oil pressure drops off when at too low idle speed. Then it rattles. The noise greatly minimizes with a good carb sync job, uneven cylinder hits make it rattle at lower engine speeds when the rockover gets erratic. The noise will be there at under 750 rpm but normal idle (1000-1200 rpm) is above that and quiet.

They all do it at least some even brand new.
 
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That noise can combine with primary and clutch dampers to make more noise, both have rubber hubs and the clutch itself can make noise with a double plate shock plate that often gets loose to fall apart, it is riveted together.
 
You have to split cases to get to primary one, yank clutch cover to get to the other two. That rivet plate gets commonly replaced with two normal steel plates and the clutch then works even better.
 
You have to split cases to get to primary one, yank clutch cover to get to the other two. That rivet plate gets commonly replaced with two normal steel plates and the clutch then works even better.

What steel plates do you use to replace the riveted plate with...just take two of the standard clutch plates (the ones used in between the fiber discs) put them one after another when reassembling the clutch?


 
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