gv550
Well-Known Member
The decompression device will be activated (1 exhaust valve held partly open in each cylinder) at cranking rpm to reduce the load on the starter, that is the purpose of the device. It will de-activate somewhere above cranking rpm but below idle rpm, likely 500 to 800 rpm. The measure-able compression will be less than if the engine did not have a functional decompression device and the specifications are adjusted accordingly. Holding the throttle wide open would have to be done manually at the butterfly, the twist grip alone doesn’t open the throttle at cranking rpm.