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

Posted by shultz_1978 on Jun 30, 2012; 10:18pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/input-on-knocking-enginge-sound-carbs-need-synching-tp4023979p4023985.html

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