dispite ALL the TALK I hear over the years, I have yet to see a TWO stroke run well inverted without some glow assist. last lad who showed up at field thought he could do it & was very frustrated. that includes lowering tanks , pressure "regulators ", idle bars etc. a hotter plug may cause other problems as well.there is also the danger of flooding and bending rods.IF & only IF well broken in you MIGHT get away with it but even then transition often suffers.