Chainsaw Repair

Setting aside for the moment the question of why it misfired in the first place, my main question was why does it set up in a pattern of fire-misfire-fire-misfire, etc?  One of the things I saw in the literature that caught my eye was that inert gas in the combustion chamber slows down flame propagation speed (this was in reference to EGR). 

With a 2-stroke there will always be some unscavenged exhaust gases left in the cylinder - unless of course it didn't fire last time.  So that means that after whatever happened to cause a condition where the mix did not fire, after that if it does manage to ignite the flame will propagate faster than otherwise. 

Going back to the original cause, my guess is that at higher rpms the time available to burn the mixture is decreasing while the mixture is getting increasingly rich due to the carb characteristics.  At some point it does not burn completely and there is a misfire - but the next time the mixture burns faster due to the lack of inert exhaust gases in the mix, and it completes the burn in time.  And the pattern repeats.

Also, flame propagation speeds generally get faster with richer mixtures, up until a point and then it falls fast.  This also fits well, because leaning it just a bit moves the 4-stroking point to a higher rpm.