I had this machine in Michigan and now I have it in Colorado at 9000' altitude. Ran perfect in Michigan but out here I went to leaner main jets. I left the pilot screws at 1 1/2 turns out and I had a serious hesitation when I punched it. I turned the pilot screws out (rich) another 1/2 turn and the hesitation is still there but liveable. When I leaned the pilot screws it REALLY hesitates. Doesn't make sense to richen when you have less air up here. Any thoughts?? Thanks 
grapeape
New member
richen the pilots, lean the main. Yamaha specs this on all recent 2 strokes.