I have seen a lot of guys have problems with Y.S. I have not. I've had two so far.

The problem I see guys having is with setting the pressure regulator. The older Y.S. do not have two needle carbs. The low speed mixture is set with the pressure regulator. Y.S. says the this regulator is set at the factory and needs no adjustment. I found this to be true on my first Y.S., a .61 two stroke. I did have to adjust the regulator on my .91 4S.

The problems I have seen other guys have come from giving that regulator screw a full turn on their first try. It is very sensitive and if you turn it more that +/- 10 degrees, you have gone to far.