And here I am having installed yet another replacement Hydraulic head for the M35 multi fuel engine, Even thouigh I installed a new "button" and retainer, I am now noticing when I press down on the button end of the hydro head , there is a measure of free play ( clearance ) in the button shaft before the shaft engages what must be the internal plunger assebly.And when I installed this head on the fuel injector pump, , there is no fuel being delivered to theb injectors. Is there asupposed to be any clearence in ths button shaft movement? Who is rebuilding these hudro heads?