Yesterday I repaired a tricky problem. I was riding stunner on a long ride. I was about 2 miles from home after about 25 miles. Like usual I was blasting about 35-40 mph. I stopped for a light. When taking off after the light, all of a sudden my bike wouldn't take full throttle. Half throttle or less it ran fine. Full throttle, it acted like the ignition was turning off.
The only problems I've had with this motor was 2 magneto coils have failed, so I was suspecting another failure. But ohming out the windings showed 350 ohm, which is normal. Since the problem seemed electrical to me, I changed the CDI box. That had no effect on the problem. It made me think about it being the carb.
But before removing the carb, I tried a few more test rides, and noticed at full throttle the motor seemed like it was vibrating more than normal. After taking a closer look, I noticed one of the screws on the rear motor mount was gone, and the other one was loose. These were the 2 screws holding the mount to the engine. 2 of 7 screws making up the fancy KW machine rear mount. None of the other screws were loose.
After replacing the screws the problem was gone. The problem was caused by the motor vribrating enough to make the carb go nuts at full throttle.
I really thought it was electrical by the way it felt.