Hi, I have brought about all the upgrades you can have for my 70cc engine (jaguar cdi, banana muffler, performance carby, iridium spark etc). So I am now looking to do some work on the engine. I was thinking of starting off by just cleaning up all the ports & polishing everything. But otherwise I am pretty stuck. I have read everything on www.dragonfly75.com and heaps on here so I'm not too much of a novice but for this job I am! What would I need to do to change the port timings to maximise power across the whole rev range? If someone could I would love to be told precisely how many mm to change my ports. Any help would be very much appreciated. Cheers.