I have inherited an early 70's Victa Super 24, with the motor between the handles and driving the blades via a belt.It has the old series 70 motor with decompressor, metal carby & spark plug at an angle on the side of the head. It starts easy & runs well. The problem is cutting the motor - I have to short the plug with a screwdriver. Any ideas on how to adjust the cutout switch on the carby?