Motorcycle Repair: gl1100, dirty air, air filter

Question
What size main jet does this cycle take.  Bought cycle and all the plugs foul out.  Have rebuilt the carbs and new coil, spark unit.  Do you have any idea what could be causing the problem?

Answer
What year are we talking about?  It could be a choke adjustment problem, it could be a float adjustment problem, it could be a very  dirty air filter or plugged muffler.  Those are the things I'd start with and see where it takes me.

Regards,
Rich