Motorcycle Repair: Plug(s) fowling on 98 Heritage Classic, stock ignition, fine chocolate

Question
Roy:  I have a 98 Heritage that has (up to late last year) been great.  Late summer, after some low spedd riding games, the bike fowled a plug,  I changed the plugs (several times) and I was still experiencing fowling.  I took the bike to a local wrench and he replaceds the stock ignition with a Dynajet (I belive) twin fire unit.  I rode the bike a few times and another plug fowled.  The mechanic then put a different jet in (I don't know what size, but I can find out).  I continue to experince fowling.  I have gone to a hotter plug (Delco) and this seems to have helped, but the problem still occurs once in a while.  I looked at the plugs and (when running poorly) are mostly black,  But if I pull them when the bike is running well, then look fine (chocolate brown).  The fowling (I belive) usually happens on cold starts.

Should we be replacing the low speed jet?

Help!!!

Answer
You shouldn't have been replacing anything.  Stock ignition works fine.  The bike all of a sudden should not need rejetting.  And you don't fix the problem by running hotter plugs.  Use the 5R6A plugs and get a new air filter.  Check the float needle.  Check your plug wires.  Is your choke shutting off the way it should.  Pull the choke starter valve out of the side of the carb and check it.  Good mechanics don't just start replacing parts to see if that fixes the problem.