carbon build up on pistons

[chgofire5sqd]

I noticed a excessive build up of carbon after looking into my spark plug opening on my 1966 stock FLH. I'm running a Champion J12YC plug in it. the bike runs great but when I was doing my routine maintenance to it the plugs were black not tan. Never had to adjust the carburetor before, the bike starts and runs strong for the 7 years I have owned it. Air filter is change on a regular basis so should I go with a different brand or hotter plug. Trying to find Harley 3-4 plugs is difficult, any suggestions. Thanks Dave

[T. Cotten]

Dave!

Have you been running on the same manifold O-rings for seven years?

....Cotten

[chgofire5sqd]

hi cotten, yes in fact I can say with certainty that they are original. I new the original owner and the bike was never apart with 7100 miles on it. I ride it pretty often and it does not cough or spit. the bike runs like a top. with that said do u think I have a small leak in the intake manifold. Correct me if I'm wrong, when testing for a manifold leak u spray water from a spray bottle on it while running. if the bike chokes or runs rough that will show a leak. Thanks for the reply.

[BigLakeBob]

O boy, Cotton's going to have Manifold Leak Class 101 with you. I've been there. Listen up.

[T. Cotten]

Dave!

Common O-rings swell enormously in modern fuels, sometimes to the point of extruding into the ports.
Modern viton O-rings may well last seven years.

Spraying anything while its running often misses all but large leaks.
Bubble-testing with air pressure is absolute: http://virtualindian.org.11techleaktest.

Testing while assembling prevents over-tightening of the clamps.

....Cotten