Technical Backfiring on One Cylinder

Hello,

I have a six cylinder 1930 Franklin that recently started backfiring / misfiring on one cylinder. I pulled all the plugs and they look fine and did a compression check and all six cylinders are in the 95 to 100 range. Any thoughts on what might be causing this?

Thanks for the help!

Bill

 

has it had the same fuel in it for over a few months? Wild guess...varnish from old gas is starting to make a valve stick, and it will stick and backfire when it's running, but not at cranking speed.

but that's just a wild guess.

 

Bad plug wire?

 

Valve sticking sometimes, or a broken valve spring. Bones

 

Also check the cap over real well.

 

Cam/lifter issues or adjustments. Don't know Franklin engines makeup. Every time I have had this it was a cam lobe gone if the plug/wire/cap was good.
SPark

 

Is the back fire more of a open field firecracker Bang? Or like a fire cracker in a closed heavy metal box?

If the compression is good,,,,
Open field fire cracker bang is sparking when valve is open and an electrical issue, usually in spark delivery.

A Closed heavy metal box firecracker sound and it's probably a valve issue.

 

Carbon track distributor cap??????