The piston SKIRT is at the bottom..Somebody tell me what the bottom of the piston has to do with the exhaust timing.....
The TOP of the exhaust port is what controls the exhaust timing...
A reed valve engine will take only as much fuel as the reed assembly will pass, no more, it can suck only so much fuel..This is controlled by the size of the transfer ports and the reed valve ....A great big carb on a little reed valve engine doesn't work as well because the air flow through the carb isn't enough to draw fuel through the holes in the venturi...You want more fuel through the engine, make the reed so it flows better..[8D]