YS FZ110S Violent acceleration and sudden stop
After the engine is started it idles well but cannot be accelerated to full throttle. When it is slowly accelerated to the lower mid range it hammers violently and loudly and then stops suddenly. This action causes the prop to slip and has worn the splines off the drive washer and the spinner back plate.
This is a new engine that is still in the break-in phase and has had four trouble-free flights lasting from 3 minutes to 5 minutes at less than 9000 RPM. The first sign of trouble occurred before the final flight when the engine quit on the runway before take off. The engine was restarted and the flight was uneventful.
No amount of adjusting the low or high-speed needle valves has any effect on this condition. Adjusting the regulator clockwise made it worse. Adjusting the regulator 2 turns counter clockwise enabled the engine to accelerate to the upper mid range before it quit.
With the regulator at that new setting, all of the fuel in the tank will run out (not drip out) through the carbureter and onto the ground while the engine is not running. The engine is inverted. The only way to stop it is to relieve the pressure in the tank. By the way, this engine has always leaked fuel from the carbureter while flipping the prop to start.
Thanks for any help.