On a point ignition piston ported 2 cycle engine there are a few things to consider. The ignition is a maintenance item and as such requires attention frequently. My experience with these is that the ignition needs to be set up every 25 hours or performance will suffer. Unlike our CDI ignition engines these point ignition engines will seldom quit but performance degrades as the pionts and rub block wears. The slightest bit of wear alters the dwell and timing. Learning how to master the ignition maintenance is critical to good performance.
The engine is piston ported and fogging out of the intake is the nature of the beast. This fogging becomes more evident when the engine is out of tune, when there is wear on the piston skirt/cylinder mating surfaces or there is excessive load on the engine at lower RPM's.
Jet the carbs according to the Rotax manual, set the ignition system to specs, eliminate piston/cyl excessive wear and pitch the prop to allow 5800 RPM WOT.
If the engine is properly set up and is in sound mechanical condition it will still not respond to a sudden opening of the throttle from dead idle without a little sag. A common sense application of power should be faultless though.
Take your time and set it up properly. It is usually not one item that causes the fault but a combination of many minor items that add up to a major item.
Dennis
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