Topic: 72 CB350 4 muffler - carb jetting help needed!?

[anton1117]

Hi!
Can you please help identify this muffler? It's not a straight pipe; its got a baffle in it. I need help and/or advice with carb jetting/setting! It runs/idles great, but starts kinda bogging down around 5 - 6 grand. Jet/needle/float setting? Muffler backpressure problem? Please advise!!
Thank you!!!

[flybox1]

Cant help with the identify of the muffler..
but,
D8EA plugs gapped to .026"
points gap .012-.016"
float setting @ 24mm.
intake and exhaust valve clearance .002"
air screws .75 turns out +/-
stock main jet #75 (though 78 worked better w/ my 4 into 2 Jardine exhaust)

forgot to ask...clean/new air filter?

after all 3k service tasks have been completed, do a plug chop at WOT where it bogs down to give you (and us) a better idea of what is going on in there...

[anton1117]

@flybox1 - Sorry, I'm kind of a newbie; What is: 'a plug chop at WOT, ...'?
Thank you for your response! Much appreciated!
Carbs have been rebuilt; air cleaner is good.
Thanks again!

[flybox1]

WOT- Wide Open Throttle.
check the FAQ's from the main page, and/or do a search for Plug Chop.
tons posted on it. 

did you do your carb rebuild?

[anton1117]

@flybox1 - no, I did not do the carb rebuild myself. But a trusted friend/mechanic with alot of experience working on bikes did it. Although I did participate in a carb rebuild with him, on my carbs once. He has actually 'rebuilt' the carbs many times in an attempt to pinpoint running problems/troubleshoot this bike! It starts right up, and runs/idles fine. He said is just kinda bogs down around 5 -6 grand. I know he has checked the points, installed new plugs, etc. He thinks it might be a jetting problem because of this non-stock muffler.

[flybox1]

yes, it very well could be, but....first things first.
Valves checked/gapped?
was timing done? is it advancing properly?
in the rebuild, were the carb slides bench sync'd?
(keyster kits have been known to have different needle tapers, different jet sizing.  did you reuse the existing, aftermarket brand?, OEM?) what size main jet is in there?
should be stamped on the side.

if all the above was done, were the carbs vacuum sync'd?

(we gotta know if all else is as it should be before we can jump into jetting to fit the exhaust.)

If YES to all of the above, ride and get into that "boggy" rpm and hold it there for a few sec letting it bog. at the same time, hit your kill switch and engage your clutch. coast to the side of the road.

pull each of the plugs and take a picture of the tips side by side. 1-2-3-4. post the pic here.