Not to hijack the thread, but in response to the reliability issue of two-stroke engines, the primary culprit seems to be the different altitudes at which the engine is supposed to start and operate. The fuel/oil/air mixture has to be within certain parameters for decent running and starting reliability. An increase in altitude (or high density altitude conditions) reduces the amount of available oxygen, which contributes to fouling the spark plugs. I used to ride the Yamaha RD-350 and TZ-250 motorcycles from Albuquerque (elevation ~5,500 ft. MSL) up to Sandia Crest (10,678 ft. MSL) and used to have to stop and adjust the needles in the carburetors four times on the way up and four times on the way down or risk plug fouling or overheating and possibly seizing the engine. About a 1,000 ft. change in altitude was all it took to affect the performance and reliability. Newer two-stroke engines with more sophisticated fuel injection systems seem to be much more reliable in motorgliders.