I recently moved to the Coloroado, near the mile high city of Denver. The XS1100 was already set a little rich for sea level at Baltimore. It runs okay at about 5k feet above sea level. I took a trip up into the mountains and got up to about 8k feet elevation. At that elevation, the 1100 simply would not idle. If I let off the gas, it would die. Additionally, when I got back from the ride that day I smelled strongly of gasoline.
The XS1100 has always been my daily driver to work. I can't arrive smelling like gas. I also plan on riding a lot more into the mountains. It was time to rejet the carbs.
I found a chart from Mikuni showing the recommended jet size changes based on elevation and temperature. With a 5k foot increase in elevation, they recommend dropping one size on the main and pilot jets. I opted to drop 2 sizes on the pilot jets since it would not even idle at higher elevation. Time will tell if this was a good idea.
I am running size 40 pilot jets and size 110 mains (stock).
The main jets are actually the ones that came on the bike originally but I had increased to 115 thanks to the new exhaust and air filter. The pilots are still one size up from stock.
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