| This is a 40mm wide piston made for the 50cc Jog Scooter, very cheap from Amazon. This is the intake side of the piston with the intake port drawn on it as it sits with the top edge of the piston at the top edge of the transfer ports which is when most of the intake begins to happen as the piston rises from BDC.  This is the same piston after I cut a hole in it for the intake I cut a rectangle in it using my rotary tool with cutting disc. Then I used a grinding bit to round everything off. Then I narrowed the bridge below the new hole for better intake flow..  The spacing for the con rod bearing was .25mm too small and so I had to grind both sides down there for the bearing to have clearance.  The ring end pins rode perfectly between my boost port and the transfers, no problem. And its rings were 1.5mm thick which is 25% less than the stock 2mm width, so it should present less friction. The new piston was almost the same weight as the stock one, just a few grams heavier. |