Topic: '76 CB750 clicking noise coming from baffle?

[dylboss]

So I've had this 750 for a week now after looking almost all summer for what I wanted.  Great overall shape.  I'm new to the stock 4-4 exhaust though on these CBs.  Got my '78 550 with a MAC 4-1.  I'm getting some sort of strange clicking noise at the baffle of the top left muffler.  I can't figure out what is causing this.  Has anyone else experienced this?

[nancy]

Not me,...but the 4-4 on the 76 750 would normally have HM341 mufflers (stamped on the top). These would have 2 or 3 (can't remember) internal baffles through the chamber and don't have a baffle fitted in the tailpipe. They have a small "diffuser" or end-cap. Is the noise from that end-cap? Pull it out and see if noise goes away to help diagnosis. I'd just guess that a "click" may be a metal component going through some "time of life" changes. e.g. rust,...or maybe it's loose!
Regards
Mark

[ekpent]

Like Nancy said most of the baffling on the HM341 is done with seperate internal chambers and the 'baffle' at the end of the pipe is basically a cap-keep out a mouse etc. Take the cap off and maybe with a good rev a trapped chunch may fly out.Next step would be to remove the offending pipe and shake the hell out of it if it has a rattle and see if anything comes out.Heavy stream of water from a hose may help out some also.

[dylboss]

Ok, thanks for the thoughts.  It does have the spiral ring type insert that I've already tightened down.  I'll remove it and see what happens.

[ekpent]

This is what the diffuser should look like on your HM341 pipe. As noted not a baffle per say. Eric   http://cgi.ebay.com/ebaymotors/Honda-NOS-CB750-Exhaust-Baffles-Diffuser-CB-750-Baffle-/320742293320?pt=Motorcycles_Parts_Accessories&hash=item4aadbaff48

[Gordon]

A hole in the baffle or the muffler can cause a "clicking" noise by letting out unmuffled exhaust pulses.  Does this click coincide with the exhaust stroke? 

[dylboss]

This is what the diffuser should look like on your HM341 pipe. As noted not a baffle per say. Eric   http://cgi.ebay.com/ebaymotors/Honda-NOS-CB750-Exhaust-Baffles-Diffuser-CB-750-Baffle-/320742293320?pt=Motorcycles_Parts_Accessories&hash=item4aadbaff48

Yes, that's it!

A hole in the baffle or the muffler can cause a "clicking" noise by letting out unmuffled exhaust pulses.  Does this click coincide with the exhaust stroke? 

Yes, it does seem to coincide with the exhaust stroke.  There are no visible holes in the exhaust itself.

[ekpent]

I am pretty sure but will ask anyway,you do have the two rubber pieces that mount the top and bottom pipes together all all is sealed well?

[dylboss]

I am pretty sure but will ask anyway,you do have the two rubber pieces that mount the top and bottom pipes together all all is sealed well?

Yes. 

The sound is coming from the tip of the exhaust.  I pulled the diffuser today and the clicking was gone.  However, I did look at the diffuser thoroughly, and I don't see any holes at all.