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1982 Honda CB750f #1 and #3 Spark but plug are black

bmaher86

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baton rouge, Louisiana
So I have a freshly rebuild carburetor with bigger jets, running a cognito single air filter and motogadget m-unit brain. For some reason number 1 and 3 are giving me spark but with I pull the plugs its not affecting how the engine runs. Which tells me 1 and 3 arent firing properly. Ive cleaned the spark plugs, tried different wires and seems to me the coils are fine, plug wires are fine and even the spark plugs are fine but number 1 and 3 are getting black and possibly not sparking enough. Or getting too much fuel and not being able to fire properly. Any advice would be greatly appreciate.


Also, I know that 1 and 3 aren't on the same coil so that narrows out the coil being bad.

Thanks,
Brandon
 
This sounds like the third restoration that needed to burn off some extra carbon from the combustion chambers and or replace the spark plugs. Perhaps the plugs are fouled out. Were the heads opened up and cleaned out? New carbs and old heads likely will result in excess carbon being released. I think pidjones simply ran his bike more and more and then all cylinders ended up firing nicely.
 
I also cleaned the carbs again, tweeked valve lash, and rinsed the oil from the tank that I had stored it with. I'm still running the same (new) plugs that I started it with. Running it more really helps now that the gas is cleaner (it ran well on the auxiliary bottle, so I flushed the gas mixed with fogging oil out of the tank.) All pipes are getting hot now. Just need weather to cooperate a bit.
 
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