A very close friend of mine is having an issue with his 78 FLH Shovelhead. It is only running on one cylinder (front). A few weeks ago it was fine but we were working other issues with the battery and the solenoid which we got fixed but now it sound like it's running on one cylinder(front)? we checked spark to the plugs, changed out the Coil just in case it was a weak coil. We confirmed that it was the front because that plug and the cylinder were not getting hot. Anyone have any idea what we can troubleshoot? It was running fine about a month ago but since the solenoid went bad it's not been good. Help please!!

 

If you're sure the coil is wired correctly, verify spark by removing the plug and grounding the shell to the engine. Look for a spark from each cylinder. If no spark it's got to be a bad plug wire, or bad plug.

Verify the plugs by swapping and see if the problem moves to the other cylinder. You can measure resistance or swap a known good plug wire to check the plug wires. The stock wires probably aren't long enough to swap.

 

Thanks for your input. We did swap the plugs and verified the spark at both wires. We are leaning more now towards a stuck valve. He lives near the bay and corrosion is a bad problem there. I have read that Sea foam is a good product for corrosion so we are going to try it and see. Will post our results.