Motorcycle Repair: 1980 cbk 750 honda, piston rings, compression check

Question
why would it keep fouling plugs mostly in #3 cylinder?

Answer
Jonathan,

it depends if the fouling is dry or wet,
dry fouling is black, fluffy looking,
caused by too much fuel or not enough
air to that cylinder. Could be a choke,
air filter or carb problem. Possibly an
ignition miss.

-Wet oily fouling could be bad piston rings,
low compression due to other mechanical problems.

-Best thing would be a compression check,
see if that cylinder is close to the same
as the others. 150 is good, a bit lower may be
okay if they are all equal.

-try switching the plug wires on #2 and #3,
I think they are on the same coil. See if the
problem changes to #2 cylinder. Could
be a bad plug cap or wire.