Not sure if this is the right place to post this, if it isn't it can be moved. Sorry for the length of the post just wanted to cover everything I did.

Took the bike out last Sunday, 48 pan low compression e model single point ignition manual advance, and it was running fine. Filled up the tank and went a block and it started backfiring through the exhaust. Pulled over and first thought was ignition. Changed out the points and condenser, fired up and did the same thing. Trucked it home and drained some of the gas out of the tank into a glass container, no water. Pulled it into the garage and drained the rest of the gas into a gas can. Wife says it stink up the garage. Had spark at the plugs, static ignition timing was on, getting fuel. No start. There was a black oily film in the carb. Blew air into the cylinder heads with both at TDC, pushrods, exhaust and intake removed. Seemed that small amount of air coming out the pushrod entry holes in the front cylinder. First thought was a cracked head, blown head gasket at one of the oil passages. Gasket was fine. Inverted the head and filled with mineral spirits overnight no leakage the next day. Did a dye penetrant check on the head because it looked like there might have been a crack on the mating surface to one of the bolt holes. No crack indication just a series of small pourous holes that made it appear that way. Reassembled. Compression check front 75lbs rear 70lbs. Differential air check 80/80lbs. Disassembled carb, S&S. nothing in there that would cause any blockage or restrict fuel, float level check out. Checked pushrods on glass, all true. Adjusted, spin tight. Rechecked full advance timing. Went to start last night. New gas. Turned the distributer about an eighth of a turn toward full advance, normal position. Backfire thru carb. Adjusted idle mixture richer moved distributer to full advance started right up. Moved it from full advance to retard and started to stall. Moved it back and it ran fine. Noticed it's smoking now. It appeared be white, but it was dark and I was looking at it in the headlight. It's acting like it skipped a tooth on the distributer gear. Pulled the gear out checked for any play or missing tooth, nothing.

Bottom end is about 15years ago. I can't remember if there is anything in the gear case that would explain this like a pin or clip holding gear in place. I know there is a keyway on the oil pump pinon gear but not sure if that would cause this problem. Any one have any idea as to what may cause this I appreciate any advice. Seems like I never have simple problems just the one in a million.

 

S&S E or S&S B carb Sounds like it's running rich (white/black smoke ) ?

 

S&S E. My thoughts also. I did enrichen it from the usual spot to get it started. It was dark last night when it ran so I really couldn't get a good read on the color of the smoke. It had a film in the carb that was black and didn't smell like fuel. I'm going to pull the plugs and check the burn on them. Thanks sqdeal. I'll keep you posted.

 

I got a bad tank of gas in Daytona a few years ago. Did exactly what your's did. backfiring, smoke, etc. While going through checking the timing, valve adjustments etc, I also found an intermitent problem with the ignition switch, it would momentarily cut off causing it to backfire when it conected again. The rollers on the stock switches wear down and also get corroded, check to see if it needs rebuilding.

 

All great solutions, good job felles.
reads like you covered a lot of area,
start her up and squirt car cleaner around the flanges, see if it has a intake leak..
ruben

 

Thanks for the suggestions. I really appreciate it. The plugs are oil fouled so I don't think it's an intake leak. One of my first thoughts was the gas because it happened right after I filled up. When I put it back together I put fresh gas from a different pump in. Chance of it being two bad batches of gas from different pumps would be a long shot. I'll check the ign switch, it does have a dead spot in the run position.

Here's the progress on it. I thought it might have been either the end play on the distributor gear or the pin on the gear sheared and it twisted just enough to shift it the equivelent of one turn. Pulled the distributor last night gear was fine and endplay was .009. A little over allowable but I don't think .002 is enough to cause the dwell to be off by that much. When I did pull the distributor I noticed that the gear was wet with oil as if it had been pulled out of sitting oil. I've pulled it before and it has had a light film on it but not like this. This kind of leads me to believe that it could be a sheared pinion gear. That's my next step. I'm going to pull the cam cover and look at the pinion gear. More to come.

 

Here's the update. Changed out the points ignition with a electronic and it fired up. Seems that there is excessive runout on the circuit breaker gear that the points won't operate correctly with. Electronic are a little more forgiving that the point type. When it started it was backfiring still. Pulled the bowl and found that when I previously removed the bowl the small blue o-ring that is on the ejector was missing. Must have fallen off when I had previously removed the bowl looking for problems. I'm going to check the gear after the first of the year. Probably won't be doing to much riding between now and then. Thanks for all the advice and support. It's good to be back on the road again.