What happens with a wide windowed piston???

The entire reason for windowing the piston is to make up for increased resistance to flow from the reed valve. Too wide would run rich. Too narrow runs lean, thus the windowing of the piston because there isn't enough time to flow the air/fuel mixture when a reed valve is present.

There are books and tons of videos on two stroke tuning. And specifically for pipes as well. I've heard Tinman's saws is a good channel. https://www.mopedarmy.com/forums/read.php?2,4561880

 
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