Chainsaw Repair

You can also make it start or stop by loading the engine so I would imagine that by loading the engine you would lower the rpm and also increase the EGT hence changing the scavenging in the process and time area needs in the process??

Yeah, sure, and it's a puzzle because so many of those factors are interrelated, which makes it hard to separate out what causes what.  The thing is that I have saws that will switch between 2-stroking and 4-stroking with very small changes in rpm - it's got to be barely 10%.  It's just hard for me to believe that some of these other effects change so drastically with such small rpm changes, while I know that the fuel mixture can.

2-strokes have been used in many applications that did not use all-position carbs, such as many little cars in Europe at one time.  There are also fuel injected 2-strokes in sleds and boats.  Do these things 4-stroke in the same way as saws?  It seems to me that if they don't, then that would mean it's a characteristic of the fuel system, not of the engine (which is what I suspect).

I spent many years studying, modifying and tuning carbs on cars, and given the way these carbs are made this is exactly the behavior I would expect.