I would also like to add that even at a high altitude here my H.T. motors that I have tried never ever did overheat. Even when ran for whole days at a time.
About two summers ago my Morini did when I absolutely tried to break it on purpose. Was testing everything I knew and was in a very destructive state of mind...I had a parasitic dragging J Shaft set up on it at the time and climbed a ridiculous incline against the Sandia Mountains here in the month of July on a very hot day for about 16 miles straight. Non Stop!! No Breaks... With a near worthless Nuvinci hub running at constant 11,000 rpms. COMPRESSION RATIO 12,5 +/- 0,5 : 1 http://www.morinifrancousa.com/engine3.htm
Any 4 stroke in this class would have had the exact same problems guaranteed
Well Nuvinci did not impress me much as the hub it self got so hot it peeled the flesh from my hand when I touched it. Had to immediately spit on my hand to get composure.
The Morini 2 stroke is a very durable engine and I could not break it. Always Ran good oil and is still brand new with cross hatch still present in the cylinder jug through and through at 10,000 miles now.. Checked and verified just about a week ago.
I no longer run it it with a J shaft and run the engine just as the manufacturer intended it to be. Never ran into any kind of issue again. I run it on many occasions for whole days at a time too. COMPRESSION RATIO 14,5 +/- 0,5 : 1 estimated a little higher now for a 21mm carby etc. At even higher rpm's !!
2 Stroke engines are awesome engines. They will run just as long and hard as the best of them. If not even better! There are many good brand 2 stroke engines besides the ones I mention out there to be had that are good engines.
I would use them all