On my Sport NT the oneway kinda slips, but thats from the excessive oil build up. I never had this problem on my other Pullstart engines mainly because of the way the pullstart is built. Not all are the same. When I go to start up the Mach nowadays I usually get one pop, but after 2 or 3 tugs it starts up. Super reliable engine and offers good power out of the box. Still want an RB C12 in that thing though.