PLY68, Small gas engines just like any gas engine need the proper fuel air ratio in the combustion chamber to fire. On a carburated motor it is tough to get the mixture just right to start. Different altitude, temperature, humidity,and choke all make a difference. The manufacture tries to design the choke to work in all the different scenarios but inevidably they can't. When you only get one compression stroke to start and run, your mix has to be perfect. That's why you have to open the throttle a bit to start these engines. The mix isn't just right.