Spark plug ?

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I'm eager to see the GURU's responses to this, but I would take a short, hard run (15 min. max), then shut her down quick and read the plugs. If they are all white/blistery, then move to the colder D9's. If they are light tan colored around the center electrode, this is ideal. Black & sooty would indicate richness and a possible need for a hotter plug heat range...this all assumes that the engine is otherwise running well... :waving:

I think a .035" gap is OK for all the flat fours...unless you have one of those hot after-market ignition systems on it...

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I agree with Mike. Best way if you don't know what year engine you have, is to read the plugs, after running a few miles. I might even go an hour to be sure. The gap, .035 is a good starter. You'll know if your on the right track, first time you open it up on the highway.

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My Honda Manual shows spark plug gap:
1980-1981: 0.6-0.7 mm (0.024-0.028 in)
1982-1983: 0.8-0.9 mm (0.031-0.035 in)
Silicon Sam posted this link in 2007 on this forum. Maybe it will help you identify your engine:
Click Here

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My thinking is that the engines are actually the same. The difference will be in the coils and primary side, and therefore probably a hotter spark on the 82-83 frame. Personally I'd go with the 80-81 numbers. However if it runs Ok then leave it.

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Given that the ignition system is a mixed bag, I would add my vote to the "ride it and see" camp

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Ok, seems to run fine. Pulled all 4 plugs after a about an hour ride and 3 were perfect, tan color around the electrode. Plug from number 2 cylinder had a black electrode. It wasn't wet and didn't seem fouled but the color was black. Could this be a carb issue? I synced the carbs but couldn't get them as close as I would like.

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To me, your plug's heat range is fine then. If you were running at good speed, then I doubt a sync problem exists for that #2, as the carbs were (are) pretty much feeding fuel from the main needle jets at that point.

I would try swapping that #2 plug with another, and enjoy another ride...then re-check the old #2 plug, and the replacement. This will help determine whether it is a carb issue , a failing #2plug, or perhaps a plug cap or plug wire problem.

There could possibly be an incorrect float level in the #2 carb., a damaged needle/seat, or a faint possibility that there is some excessive wear on the main needle/jet bore also.

I believe those carb slides employ a spring and thin diaphragm, not positive though. If they do, you might inspect the diaphragm for holes/tears, and confirm that the spring and the slide itself are serviceable and work freely... :waving: