Ignition coil issue?

jwing

CB750 Member
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Pennsylvania
I have a 1981 CB750k that has some hesitation and sputtering under high load, and I’m also continuously getting a black plug on cylinder #2 (even after new plugs).

It seems to start up and idle fine, and even runs pretty good for the most part. Cylinder 2 is getting hot right away on startup, along with the rest of the cylinders.

I’m thinking it’s a case of weak spark, especially under load. Could this be caused by a bad coil? I checked resistance across wires and plug caps and they seem okay. My only doubt for being a coil is that theyre dual output and have a wasted spark, so I would think #3 would be having a black spark plug as well if there was a problem with the coil.

Any thoughts?

-Valves are adjusted
-Compression is good (150+/- psi)
-Carbs have been cleaned several times, although I need to sync them properly
 
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