1976 Honda 360T Carburetor Trouble

| 9/5/2018 8:25:00 AM

Motorcycle Classics tech expert Keith Fellenstein

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Q: I have a 1976 Honda 360T in very nice original shape with just 13,000 miles on it. I just had the bike tuned up at the local Honda shop (new points and condenser, set the timing, adjusted the timing chain, set the carburetors, new plugs). The carbs were not taken apart and cleaned. Upon getting the bike back it fired right up and idled. Taking it on the road for a good run, however, I noticed it missing on the right cylinder, with a "popping" from the right exhaust. Back home, I took out the plugs. The right side plug was fouled badly with black soot, while the left side was a nice medium brown. I tried a new plug and rode it again, but I got the same result: a fouled plug. Using a "color tune" kit I had gotten from England awhile back I was able to see that the plug color changed with increased rpm, from blue to yellow (hot to cold, hence, the fouling). My question is, what could be causing this? The points are new, as I said. I'm wondering if a clogged jet or other carburetor problem on the right side is the cause.
— Bill/Rhode Island

A: I think you've hit the nail on the head. It sure sounds like carburetor trouble from the symptoms you describe. First, I'd try to drain the right side carb and see if there is any clue there. Then I'd pull the right carburetor and make sure it's set up correctly. Water precipitated out of the gas/alcohol mix we seem to get these days will often pool in the bottom of the carburetor and get sucked into the main jet at wider throttle openings.

9/13/2018 10:54:51 AM

What, the local Honda shop didn't test ride the bike after the tuneup? I agree it could be the gas, however check the vacuum piston rubbers for tears as well. Hopefully the main or slow speed jet didn't fall out. Also, I assume they timed the bike with a timing light for one piston, and altered the point gap for the other piston.

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