Less fuel needed for higher elevation because of less O2.  Smaller jets, more space on the needle valve, etc. will help you maintain the correct air/fuel ratio at high altitudes...

Interesting read on it for Bing carbs.... the HP chart is also interesting

http://www.horizonsunlimited.com/tech/carbjet.shtml

141.3 main? might a been off one key on the keyboard - bet thats a 152.5 ?

Reelthing wrote on 12/24/07 at 07:33:59:

had a dyno #145 main = mikuini??
had stealer do the tuning(was the 4k service) they got a tuning meter of some sort tech wrote 141.3 on job ticket..dont sound right to me either

Your carb (standard mikuni) is altitude compensating. IAW as you go up in altitute it leans itself. The slide get pulled (sucked) up by the amount of difference in airpressure above the rubber diaphram vs below. As you go up in elevation you get less of a pressure difference between above and below the diaphram so it does not pull the needle up as high. The needle, being tapered allowes less fuel to get sucked thru the jet so the mixture stays fairly constant. The ideal being about 14:1. I've been over the Berthau Pass in CO (over 11000 ft) with a Bing eguipped car without a problem and have flown Bing carburated lightplanes to 18000 ft without changes.
So I wouldn't do anything (maybe a mixture screw and idle adjustment) unless you were going to be living at that elevation. If your bike has over 20000 miles I would put in a new jet and needle since there is a slight amount of wear on both which would enrich the mixture. Also would be good to clean the slide and bore from deposits for smoother operation.