What do the fouled plugs look like? Are you using any oil? Any significant blow by/smoke out the exhaust or in the crankcase?
Charcoal/ashy, but sort of dry, in appearance would likely be too much fuel. Look at your float bowl heights, float needle valves, or even your air filter.
Cruddy possilby wet and/or Oily in appearance would likely be oil fouled, so valve seals or bad rings.
If you have a 2001 or early 2002 1200, they were/are know for bad rings. Search the site.