Vintage and Classic Hondas

Clunking below 1700rpms?

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rusche

Clunking below 1700rpms?

I just picked up my first bike, an 82 CB750K. Pictures to come later.
Its got a clunking coming from the left side cover. Ideas? I used a stethoscope to verify, its definitely in there. Sounds similar to a knock. Aparent at idle, goes away around 1700-2000+ rpms.
Its got good oil pressure, no metal or contaminates in the pan or oil.
Carbs arent synched 100%, but close, I cant imagine that would make this much noise.
Other ideas?

Thanks
Thomas

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Re: Clunking below 1700rpms?

Administrator

Welcome to the forum. I am not very familiar with the DOHC models. However if the carbs are not synced perfect. It will sound like the engine is about to blow.
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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
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Peterwh

Re: Clunking below 1700rpms?

Personally, I think syncing the carbs is about the most under-rated maintenance task on these bikes. Getting the carbs synchronised can make a huge difference to the way they run.

Rodgil

Re: Clunking below 1700rpms?

In reply to this post by rusche

Fairly common on DOHC models, usually nothing serious, just backlash due to an uneaven idle. Can be improved by syncing carbies. Use the search box (right hand top corner on the forum) and search "knock at idle" for more answers

Dw07u

Re: Clunking below 1700rpms?

I'm glad he asked that question, I also have that noise, but closer to 1400rpm, and after some youtubing i hear it on other DOHC bikes too, the last mechanic I spoke too said it's the cam chain rattling, but nothing to worry about... But once my bike is all heated up, its gone...

Dress for the fall, not the ride...

rusche

Re: Clunking below 1700rpms?

Mine does it off idle to around 1700. 1700-3500 its there but you have to listen for it, much quieter. It doesnt change with heat though.

free2ride

Re: Clunking below 1700rpms?

ya, mine sounds like it has a death rattle until it's warmed up. still worries the you-know-what out of me when I start up but it disappears into a beautiful purr when warm.

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Re: Clunking below 1700rpms?

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You guy's sure don't want to hear a cold automatic run. They rattle like they are filled with rocks.
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