Motorcycle Repair: Honda CB550K - 2 cylinders not firing, honda fours, plug caps

Question
Hi Bill,

I know that we've spoken before about my old S90.  Now I've got a CB550K that was runningwell.  It was "idling outside the house one day and when I came back, the right two cylinders were no longer firing.  I checked output from the petcock and it's feeding both sides.  I drained all four bowls and fule is coming out.  I am not a mechanic, but I'd like to use all cylindersw if possible.

Thanks!

Phil

Answer
Phil, Honda fours all have two coils and two sets of points and condensers. The points need cleaning and readjusting so the ignition timing will be correct. Condensers can fail and then you get a LOT of arcing across the points when they open and close. You can watch the points with the point side cover (big chrome one with two screws) off at the end of the crankshaft and engine running.
Not being a mechanic, cleaning, gapping and adjusting the points correctly may be beyond your scope of abilities.

If the points get corroded or the gap closes up, then the coil that is attached to those two cylinders won't fire.

If the condenser fails then that coil won't fire.

If one of the spark plug caps fails then that coil won't fire the two plugs either.

If one of the spark plugs fails the coil won't properly fire the plugs, either. Both plugs have to be securely connected to the spark plug caps, which twist onto the ends of the plug wires. It is a closed loop, so anything that fails within the loop prevents one or the other plug from firing.

The coil electrical connectors are underneath the fuel tank, so you have to pop up the seat, disconnect the fuel lines and remove the rear tank mount to get the tank off for inspection.

More than likely the problem is with the points and condenser. Point gap should be about .012-.014" at the high point of the point cam. Sounds like it is ready for a tune-up.

Bill Silver