If a GY6 125cc or a 150cc motor swap still isn't enough for you, then you need to get the GY6 180cc 63mm Big Bore upgrade for your swap. Complete with machined crankcase this is the easiest way to upgrade the GY6 from a 125cc or 150cc to a 180cc displacement. Thus giving a higher top speed and much better acceleration. The kit includes all parts necessary to install. No further machining is needed.