Motorcycle Repair: burning plugs, high altitude, dirty air

Question
I have a 1994 MZ with 500cc rotax. It has developed a problem burning plugs every few hundred miles. I thought it was a fuel problem, but I was wrong. Plug is burning fine. Touch of black tan edges. I may be driving and poof...no spark. It may start, it may not. Might get 50 miles out of a plug. Compression is good, and the bike has 6200 miles on it only. I have checked wiring and am lost as to the problem. Any suggestions what I can look for would be wonderful.

Answer
Hi Gary.
 Is this engine the OEM engine for this bike?  The reason that I ask is that Rotax builds engines for ultralight aircraft.  If this was an engine replacement, then that could be the problem (an engine designed to be at high altitude on a ground vehicle).

If this is the original engine, then the problem could be a mixture issue from dirty or mis-adjusted carbs.  They may need to be cleaned or you may be overdue for a new air filter.  A dirty air filter will make some engines run lean and it does seem like you are running a little lean.

There is also the possibility that the plugs that you are using could be a bit hotter than the factory recommended plugs.

 The repair manual will list the recommended plugs as well as maintainence specs and schedules.

Start with that and let me know what you find.
Good luck.
FALCON