A little more information would help. Year and mileage of the R1200. Describe more what happens when the engine "slows down and dies". When was the last time the fuel filter was changed? How long does he wait before the engine will restart (is it 15 minutes or is the engine completely cooling down)?
"That's right, you're not from Texas, but Texas wants you anyway." -LL
2001 Z3 3.0i Roadster (Topaz Blue Metallic, 5-speed manual, Sport Package, CD radio, heated seats and mirrors, non-power top via special order)
"Beemer" is for my BMW motorcycles - '13 K1300S, '95 R1100RS, '88 K75S, '75 R90S (gone, but not forgotten).