Try warming up the motor with a hair drier, heat gun, etc. This will allow the motor to turn over more freely. Sometimes two washers under the glowplug will help. Todays motors are designed for using electric starters. Clearences are built into the design of the motors to allow thrust in both directions. That is why there is a steel washer washer behind the prop hub, to prevent wear when starting the motor. This is one fine motor once you get past the brake in difficulties.