The the crankshaft is a NCY BWS100-250 , the quality is good and the actual stroke is 50mm, so the total capacity is roughly 123cc with that Ø56mm cylinder. The cylinder has to be worked and cleaned deeply, but if you are able to do some minor manual work, no problem. The exhaust exit is only 22mm, I enlarged it to 30mm to have more power. The price is excellent.