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input on knocking enginge sound, carbs need synching?

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theban

input on knocking enginge sound, carbs need synching?

I just bought a 1981 cb750F thats been sitting outside for a few years, it runs good and all, but has a rythmical knocking on idle and low rpms.

here is a video where I try to show the noise. I am hoping its just my carbs that are out of synch and that the backlash causes the noise. But I would love for some more experienced ears and minds to ponder this noise.

I have constructed an experiment where I go to about 30mph and kill the ignition to listen to the engine and I havent heard the distinct clanking when doing so. Could this point towards carbs out of synch as the origin?

I have tried to adjust the cct but I suspect the springs are out of shape seeing that the bike hass 93000 Kms on it:)

any thoughts?!
http://www.youtube.com/watch?v=YVPpScwzbfM

thanx
Eyvind

shultz_1978

Re: input on knocking enginge sound, carbs need synching?

theban wrote

I just bought a 1981 cb750F thats been sitting outside for a few years, it runs good and all, but has a rythmical knocking on idle and low rpms.

here is a video where I try to show the noise. I am hoping its just my carbs that are out of synch and that the backlash causes the noise. But I would love for some more experienced ears and minds to ponder this noise.

I have constructed an experiment where I go to about 30mph and kill the ignition to listen to the engine and I havent heard the distinct clanking when doing so. Could this point towards carbs out of synch as the origin?

I have tried to adjust the cct but I suspect the springs are out of shape seeing that the bike hass 93000 Kms on it:)

any thoughts?!
http://www.youtube.com/watch?v=YVPpScwzbfM

thanx
Eyvind

Hi
I don't know that the carb's will stop the noise, But if you have not had the carb rack off to clean them it would not hurt any thing. I bought and rebuilt a set for my 78 and could not believe the difference it made. The bike sounds and runs alot better.

The rebuild is not to bad on your carbs I did a set About three months ago. It will give you a chance to check all the internals.

Good luck

Simple if some one else can, why can't I
Jamie

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Re: input on knocking enginge sound, carbs need synching?

Administrator

In reply to this post by theban

If the noise stops when, you give the engine some throttle, then it is the carbs needing synced.
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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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