Motorcycle Repair: 1971 CB450 overhead cam twin, air fuel mixture, ground squirrel

Question
Low milage/seldom used bike. Seems to be firing on only one cylinder. Have checked plugs & points. Did this once before. When I was riding it all of a sudden a large amout of carbon came out with a bang and then it ran fine.  Could a valve be stuck.

Answer
There's not any extra room in the cylinder for a valve to stand open.  The valve would hit the piston and bend the valve and it sure wouldn't run normally after that.  Could be a dirty carb, mouse nest in the air cleaner, or maybe even a plugged exhaust pipe.  I had a bike once that a ground squirrel built a nest in one pipe and it was stuffed with walnuts and acorns and such.  I could not figure out what was wrong with that bike for the longest time.

The loud bang you heard was the raw fuel that had been pumping through the exhaust ignited when that cylinder started to fire. A non-firing cylinder could be a lean or rich air fuel mixture if the ignition is working correctly. Does it start and run good with the choke on?  Or if you shut the fuel off will it eventually run good for a little while? These checks can tell you if it's a fueling problem or maybe you still have a ignition problem.

Regards
Rich