Those ebay kits are working OK. You must check the ports as they can need some cleaning up. The last one I got was terrible.
Mr.Sampson, Where do you see a big bore kit? LASleeve discontinued them.
MacDizzy is a super smart guy but when he opened one of my motors, he learned alot. We chatted about it.
The big bores did make a lil more bottom end power but reliability is not good.
Porting is how to make more rpm's and power.