Hey I lived in Flag for 18 years. You may have to dink with the carb jets or get bigger ones but I think if you have the old NT carb you can probably just move the C clip up or down to start with. Also if you really need help find Mr. Garrett Van Hylkama he lives on Apsen street (i think 712) and is at Macy's coffee house most mornings on one of his beautiful bikes. He has about 40 bikes and even some 2 stroke cars (old SAABs) if anyone can help you get it running good at that altitude it would be him. He's one of the best bicycle resouces in the whole town and state. He is also a master mechanic who knows tons about 2 strokes and anything mechanical. Also Tim Vecoe from Tim's auto electric if these guys can't fix it they will fix it where no one can fix it LOL. Really they are great resources and would probably be happy to help or at least give you some pointers or ideas. Tell them "Hippy Kenny" says hello. I llive in Oregon now and have not been able to go back to see them for years but I know they both would never move or leave Flagstaff. Good luck, Ken Hill AKA sideshowbob.