Having a running problem with my marder , will start fine idle fine , pulls away fine but soon reaches a speed not very fast , and wont accelerate any more as if its only open half throttle , have checked that the carb is opening full throttle ok . have re gapped plug.. carb settings factory . ive removed the head and there is bit of scorring on the piston, exhaust side . the inside of the head has few shiny bits, few dull bits?? which should it be .. not been able to determine what engine it is. its a zenoah i know that , numbers on head are 1148 numbers on block are 1140 piston measures 32mm across 30 mm depth can anybody help me ???? not sure of previous history of car bought second hand :helpsmilie::helpsmilie::helpsmilie::helpsmilie::helpsmilie: