Motor wont start .Hi Imay be thick but what stops the back flow on a old 160 ,when piston goes down ,well ok on the old iron horse motors there where a reed valve flap to stop back flow,yes i under stand on the compression stroke it fires ,does the piston position in barrel cover over the intake port to cut the flow from going out the carb ,just remebered the vaccum stop valve opens to let air come in for the commpression stroke it closes for the firing stroke,perhaps the valve is stuck or spring in it shot causing the motor to have less commpression when requird for the firing stroke ,motor wont start any other ideas
