I drove my ‘41 from the storage unit to home about 4 miles, once warmed up it backfired all the rest of the way. It also backfires while it idles. I had Skip rebuild the coil and Charlie NY do the carb two years ago, Tubman condenser, helmet has not been touched. Previous owner put new plug wires. I suspect a valve hanging up as the Reds headers have the paint burning off the driver side but not the passenger side. I have a vacuum gauge and a pressure gauge to check fuel. It has an electric pump and mechanical pump.
As soon as it stops snowing
I’ll get it out into the driveway to trouble shoot).
Is there a checklist of where to start?