That compression is good Both cylinders within 10 % of each other If you didn't turn down the accelerator pump on the carb do it Some people don't understand that an S&S carb is a roll on style not like a CV where the vacuum pulls up the slider If this doesn't get it drop the high speed jet one size Good luck

 

ok, one question. Did you ever check what kind of spark you have on each cylinder? If not ignition, I would guess it would have to be something mechanical. Maybe your exhaust valve on the rear cylinder isn't opening far enough?? this would allow for plenty of compression, but wouldn't allow the exhaust gasses to escape fast enough, causing a black sooty plug.

 

sqdealgeorge
No, I haven't been in the carb yet, but I'll take a look tonight. I've sort of discounted fuel problems since this seems to be one cylinder only.

d slat
Actually the plug is not dry and sooty, it's wet w/ gas, which makes me think all of the gas in the chamber is not getting burned. I just can't figger out why.

I have started carrying a spare sparkplug and 13/16" socket though.

 

New development - rolled out the bike to come to work this morning, (I drive it everyday), and it turned over twice, stopped, all the lights went out, and that was it. I didn't have time to check anything, so I just rolled it back in the shop, put the Battery Tender on it, and took the gas guzzler to work.
Man, it just keeps getting better.

 

I had a 69 FL the rear plug would get wet and foul out. Tried everything. Then I replaced the charging system and it went away. Just my two cents.