One way to test for the right plug is to watch how the engine acts when you crank it. Does it sound like it is gargling or like it is sloppy full of fuel when you slowly advance the throttle? Does it want to die out on you when you do that? The A3 fixes this and gives a better burn, so much more power.

If you have real problems running one of these engines, you may have a carb or bearing problem. Normally, these are well running engines that are very forgiving when tuning them. The crankcases don't load up with fuel as much as other 2 strokes, or they burn that excess fuel off better, one of the other.

Some Evolutions were shipped without the O ring for the carb. There was a trouble with those engines a couple of years ago. This was mostly limited to the .61.