If we go with 285 or especially 310, the easiest bump in power would be to go to methanol. $40 jet kit and you do not have to open the motor and replace parts.
Mike, I agree that the kids would be slower than last year’s Jr1 animal but they still may be as fast or faster than this years Honda if they use the engine package and spec gear they were taking about.
This is one of the reasons I think that age group would be ready for a world formula motor. I may bolt on my WF to Tyler’s kart and let him see the difference. (Rev limiter connected). 4 cycle Briggs TAG!