1980 Honda CB650C Exhaust

[canadianpatriot]

Greetings Gang,

I am trying to bring my 1980 CB650C back to stock. In that light, I have an opportunity to purchase a stock exhaust from a 1981 CB650. This is the 4 into 4 (2 on each side) exhaust.

The question is then, would the stock '81 exhaust fit properly to the '80 Custom engine and frame? Are they different somehow?

I currently have a 4 into 1 exhaust (installed by PO) and it just causes constant havoc with my jetting.

Thanks for your time!

[Volker_P]

I am not aware that there are differences between the 80 vs. 81 4-4 exhausts.

Anyway I doubt that the exhaust alone (unless it is plugged) would cause that severe issues:

(Bike bogs and has no power on 1/4 throttle onward.)

Nice to have a 4-4 for a reasonable price so get it but better do not expect that the bike will run just fine then.
Stock airbox and jetting?
Some PD50 carbs might still have air cutoff membranes. Your issue might come from cracked air cutoffs.
Check at outer carb below circular cover, if there is no membrane and no bores through the carb body this is no issue for you.
Membranes are hard to get and you would have to split the carbs so one could simply plug/solder the corresponding air channels as described somewhere here in this forum (see viewtopic.php?f=4&t=722 (page three there) and viewtopic.php?f=4&t=8781&start=6).

[canadianpatriot]

Thank you for the quick reply Volker!

I do have a stock airbox. My mains are up to 95 and slow jets to 40. I have read here recently about changing/shimming needle jets so that was my next test. Then I found the stock exhaust for sale and thought it might help.

I have never paid attention to the air cut off valve and membrane. That will be my next step then, to inspect that.

Thanks again for the helpful advice!