Hi mate, the oil could be rebore & rings, new piston if its badly scored. Check the timing either too far advanced or too far retarded. Check valve clearances (tappets). Check mixture, sounds very weak but is not the only cause of popping & banging, float height, needle position, fuel delivery, inlet manifold split. Prolonged use of throttle while stationary wont help(red exhaust)Check each one at a time & hopefully you'll find the gremlin. Another engine might be the answer though.
Chris P.Duck
January 2011
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