Shovel Weak Spark
 

My 1979 FXE 1200 has been fouling the spark plugs for a while now and I can't seem to solve the problem. Within 50 miles with new plugs they foul out with black soot; it's not an oily plug. I've removed and cleaned the carb. I looked at the spark (with plugs out and one plug grounded) and it looked weak, couldn't even hear it "snap" so I put on a new coil. I checked the spark again and no change. I've been running this carb for over 40,000 miles and this is the first problem. What could be causing the weak spark? HELP!!

If it has enough spark to crank and run...seems the black soot is your problem...might want to check that carb a little closer.

The carb has been cleaned completely and a one-size smaller jet was installed. No change. This carb has run fine with the larger jet for over 40,000 miles. I think the weak spark is causing the fuel to not burn completely resulting in fouled plugs. What would cause a weak spark?

Piss Poor air cleaner element?
Drag Pipes?

I have never been able to test the Strength of the Spark. if it lights...it works.
Battery Voltage??

Clean air cleaner element, mufflers. I guess I'll have to take it to a shop tomorrow. I'm at a loss for what to do next. Oh well, just another day with an old Harley. I guess with 92,000 miles on it I shouldn't be surprised, but that's what makes it fun. lol

What kind of carb do you have?

I would suspect choke/enrichener stuck on before ignition. is it belching black smoke?

Run a finger around the inside of the ends of the exhaust pipes, the residue have a sticky feel to it ? If so you may want to drop a pipe or the carb and look at the valve guide if it's wet looking you got oil coming by the guide in the heads. Happens when the guides get enough miles they start to work loose in the heads. First indicator is fouling plugs like your doing for no other reason you can find. In the early stages the plugs look soot fouled and smell like gas.

Clean? Or New?
Friend had the same problem when he changes to a New air cleaner element...Problem was. He took out a Dirty K&N that flowed much better than the Sponge he put in!!!
Solution?? Replace with used [knock the debris off] K&N and Ride Happy...
This is a No Shit deal, and I will introduce doubters to the guy...

I'm running a CV from a 91 HD with a clean K&N. It's been on the bike for many years. I'll check out the choke/enricher as suggested. That may do it (fingers crossed). Thanks for all the help!