---

Well the older two strokes are pretty inefficient by design... When the piston moves down the cylinder to the bottom, both the intake and exhaust port are open at the same time for an instant and some of the unburned intake charge does pass right through the cylinder into the exhaust. My guess is this is what you're seeing if you haven't noticed a change in the performance of the engine...

I feel the same as you and that's why I've limited my search for a replacement engine to a DI model as the direct inject eliminates the intake port being open at the same time as the exhaust, and is one of the reasons those engines get such clean emissions ratings.