Tony...I converted 4 of those, all were 550s....The ignition is a flywheel mag, fires every revolution....Normal rotation using the flywheel ignition is clockwise viewed from the front, if you make it that way it will need a pusher prop....I made 2 of each, all 4 had electronic ignition with syncro spark...the carb is a Zama, not very adjustable...You can change the carb to a Walbro 2 stroke carb, there's a pressure fitting in the case that works for the pulse...doean't take a very big carb, a WT76 works just as well as an SDC80...
Pe...We run our GT80s on glow fuel with about 25% nitro and 6% synthetic oil, no problems after 2 seasons....I have a 289cc twin here that's always run on methanol and 8% Klotz with no nitro, still looks new inside....All these have fairly wide roller bearings, probably at least as wide as the pin diameter....