Sooty plugs

J

jomama

New Member
OK Lads I am looking for someone that can maybe help me out here. On my 76 cb360, I rebuilt the carbs over the winter and all has been fine until of late. Its started to break down at 4 grand . It starts and idles well . I just looked at the plugs this afternoon and they are pretty black which would indicate a rich condition. However when the carbs were rebuilt as far as I can recall the original mail jets were like 110 and the replacements in the kit were somewhere in the 80s and I thought this is going to be a lean result. Now I am running with no filters at all. I know its a bad idea but I just wanted to add this to eliminate the diagnosis of wrong or dirty filters. Now with smaller mains and no filters I am baffled as to why the plugs indicate a rich condition. Any help appreciated.
 
Both plugs? Are the plugs dry and sooty or oily/greasy black? Oily is a different problem and could mean valve guides/rings/seats.

Or maybe its just the float level or pilot jets are clogged w dirt.
 
Black plugs aren't always a result of incorrect fueling. Bad compression or incorrect timing can also give a bad plug reading. Check compression and timing first, then worry about fueling.
 
It's a 360 thing, they all do that around 4~4.5k without stock airbox
If you get it past the 4~K missfire, it will break up real bad around 7K when it goes super lean
You should have 68 primary mains and around 110+ secondary mains, depending on exhaust system
I'm going to be making some 55 primary mains next week
 
I will get the old comp checker out and see what ive got. Ya know, I have had bikes with 3 sets of points and I could never inderstand the complexity of the multiple point system. Lets face they made V8 cars with only 1 set forever and they ran just fine. Its like the cars of today with a coil for every plug. Give me a break , once again V8 1 coil . It does not lack for power and runs like a raped ape. For some unknown reason, the misfiring at 4 grand has ceased . I have some carb pods on the way and I will se what becomes of that. Timing may be the culprit here. I static timed it but never set it up with a light which I will do also.
Unrelated, it does seem like the odometer is grossly off and the speedo as well and it centainly looks like a stock front wheel setup are these units known to be in error?
 
Yep but your old V-8 never made even close to the bhp/liter your old bike is making
If it did, a 350 Chevy would be pushing around 600bhp stock instead of about 180~250 (around 50 bhp/liter)
360 is rated around 100bhp/liter as are most 1970's bikes even after EPA regs

It's like comparing apples to alligators
 
Yep, the bike is the apple the car is the alligator (big, dumb, heavy and can kill you pretty easy) ;D
Speedo is not particularly accurate over 30mph, but, magnetic drive works and is cheap to produce
What size tyre is fitted, stock 3.25x18 will give closest to correct readings for odometer
Motorcycles are not particularly complicated even with multiple carbs, points, 4~5 valves per cylinder, it just that automotive designs were built for unskilled workers to assemble.
They are big and heavy but really really simple plus because of relatively low power outputs and rpm, very tolerant of incorrect settings
 
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