Greg, had no additional head work. This problem started after the engine casing had to be replaced. Not sure if related. I asked D&D if it would have involved anything that could affect the valves or seals. They said no and that a bad valve guide seal is unusual for a bike with my mileage. Still, it is the best conclusion I've heard that fits the symptoms.
The casing change did cause some oil to get into the right side of the airbox. The breather is different on the new casings from my original. Running the oil level in the lower range seems to have helped this. I thought this might be the cause of the right plug fouling but the plug situation has remained the same.
