Recently I spoke with a close friend of the family who is also a mechanic. For over 10 years he worked on small engines (mini-bikes, snow-mobiles, mopeds, lawn-mowers, generators, etc.). For a short time in the 1980s, he was a dealer of SACHs engines in Oklahoma.
I asked him about the 70cc performance upgrade from Athena and he mentioned that I could do essentially the same thing by putting TWO head gaskets between the engine head and the lower part of the engine. Evidently, the extra space causes the engine to be larger and therefore does basically the same thing as the performance kit, for $4.00-5.00!!!!!
He said that if I did decide to use two head gaskets that I needed to make sure that I torqued the screws correctly to ensure that I do not get any leaks. He estimated that I should be able to increase my speed by about 25% (currently ~25, I should go to ~33mph).
Has anyone out there ever heard of this? or tried this? For the price of one head gasket and a little bit of time, I think I will try it!!!! And the best part is that because I will not be putting on a new head, there is no real "break-in" period. Besides, he said that if I did not see the type of power increase that I wanted, I could always spend the money and put the 70cc performance kit on later. It is too bad that he does not live close enough to show me how to do it.
The next time that I talk with him, I will ask him if I it is possible to put on the Athena performance kit AND the extra head gasket to increase the engine size even more.