A few days ago we went over the mountains. In one day we went over a 12,000′ and 2 10,000’+ passes. Everyone was concerned. My carb is a Linkert M41L. When we started to climb I leaned out the carb to get more air to it and the motor handled the altitude well. The next 6-8 days we went up and down and I adjusted as I rode. My concern was to not get it too leaned out. So I watched my temp readings and adjusted as I went. There was some time when the bike had a stutter at high speed (47 mph) but it ran cool and had power so I lived with it. My temp probe is on the rear cyl head bolt . I can move my leg or use my hand as a shield to deflect more air onto the motor. By moving my leg I can raise the temp probe 20-30 degr in 2 minutes and bring it down slowly. Once I learned about this I monitored my motor heat the entire ride. The afternoons were bad because they would get hot and the motors did not like the long hot rides. Remember, the VL motor has a total loss oil system and I was dropping my oil at night. The oiler seemed to work well but there was no oil getting to the primary chain. So each night I would take my primary cover off and oil the primary chain and rear chain. After a few days the chain stretched so I also would adjust the chains at night. OK, back to the heat and motors. At about day 12 I realized I would struggle most afternoons with a hot motor. So I began to drop my oil at noon and the motor ran better. I was pumping oil all day and so would also drop the oil at night. I also have been adding a syn 2 stroke oil to the gas to help with additional internal oiling.