[blueboy5000]

Well if you're not familar with what a 'woodruff key' is, you should probably not use your 150cc engine as a learning process! (it's a little rectangle of hardened steel that sits in a groove on a crankshaft)

A 63mm cylinder requires BORING of the cylinder, which requires HONING of the cylinder as well (unless you purchase the "jug" pre-bored and honed) milling of the jug may be required to fit properly, as well as a MINIMUM of 2 base-gaskets.

This is NOT a first-time try and see experience, crank and BBK is the most difficult mods possible to a gy6. Removing the old crank bearings requires use of a torch. Reinstalling the crank bearings requires FULL diss-assembly of the ENGINE CASE and full cleaning, as you will have to heat the block in an OVEN and freeze the new bearings in a FREEZER or DRY ICE bucket to make them fit. I have found no way to accomplish this without use of heat and cold.

Again I state this is a VERY DIFFICULT mod, not for the inexperienced.

Your 232 engine will require a much-modified carb, bigger cam(s) and would greatly benefit from improved CVT and OIL COOLER as well. A 232cc runs much hotter than the stock gy6 157.