I am working on my first engine conversion it`s a 31cc Ryobi. I am installing a new ring to freshen the engine seal. My question is what other performance mods can I make to this engine to improve it`s power output. The engine came with a WT 340 Walbro carb and has the desirable cylinder, no porting slots. I have read on the forum about guys milling the bottom of the cylinder to up the compression ratio. Is this an advisable mod ? If so , how much is acceptable? Any information will be appreciated.