The 230 is kinda gutless by nature and needs every little bit. It is amazing how far out of timeing you can have one and they still run, just odd, REAL odd. I had one that was some where between 45 and 90 degrees out when I bought it and it would still move itself.If the timing checks ok you might have a issue with the carb or governer.If it has the hood mounted aircleaner, make sure the hose is not kinked. Had one get turned around kinda funny and when you shut the hood it would twist and kink, robbing the engine of nough air to propel you much faster that 20mph. If it is the governer, it would be simple enough just to remove the two screws holding the flap on.