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Noisy Primary Chain

itcan

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I have a 1981 Honda CB750F. When starting the engine, there is a knocking sound coming from the center of the engine - in the area near the starter motor mounting bolts. On inspection, it appears that the Primary Gear Chain Tensioner is worn. I could not find a new tensioner and the part is no longer available through Honda. I then reassembled the engine - correctly to spec. Upon starting up again the noise has increased. If you rev the engine, the noise goes away at about 2000 RPM. To my mind, it seams like the increased RPM increases the oil pressure and thereby increases the Primary Chain Tension. Or am I wrong in my diagnosis? Any idea where I can get a new Primary Chain Tensioner?
 

itcan

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Seems like this is a sleepy forum or my problem is too technical!!
I stripped the engine completely and found the inlet and exhaust timing chain tensioners to be finishes. In addition, four of the exhaust valves are slightly bent and one valve cotter is missing. So.... anybody know where I can get timing chain tensioners, exhaust vales and a cotter from?
 

Motorhead

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My source of parts was always davidsilverspares.co.uk.

Sent from my A0001 using Tapatalk
 

Bradplaysguitar

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Engine noise

Seems like this is a sleepy forum or my problem is too technical!!
I stripped the engine completely and found the inlet and exhaust timing chain tensioners to be finishes. In addition, four of the exhaust valves are slightly bent and one valve cotter is missing. So.... anybody know where I can get timing chain tensioners, exhaust vales and a cotter from?

Hey did you ever solve your problem? I think I’m having the same issue on my 1981 cb900f
 

grepper

Old Bike Nerd
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The tensioner on the Primary change runs off of oil pressure, so they can get noisy at low idle. Sometimes just syncing the carbs will smooth is out, as a smoother running engine will produce consistent oil pressure.
 

Skelee

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Some sites for parts
4 to 1 honda
Cb750 supply
Fortnine
Dime city cycles

Have you adjusted the cam chain?

Sent from my SM-A520W using Tapatalk
 
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