42,000 miles, never dropped,timing belt replaced at 20,000, live in the Colorado mountains, no other bike issues. I ride for maybe an hour - no problems. I'm up around 55 usually calling for power - the bike looses power like a couple of cylinders are shutting down. It can rebound and surge for maybe 10 seconds then looses more power. Engage the clutch, engine dies. Roll to a stop. Turn off the ignition. Turn it on. Starts right up! Runs fine for maybe 15 minutes -starts all over again. Same pattern inevitable - run fine/loose power/surge/loose power/dead/starts right up. First started just after a fillup but have run 2 tanks of premium gas with no change. Mechanic wants to search for a loose wire but doesn't make sense to me with such a predictable pattern. It's dangerous! And I want to sell but not with this problem!

Sounds like a fuel problem to me. Might try changeing the fuel filter & running some Seafoam thru the fuel system.

Check the fuel pump.