Or research Dial-A-Jet. A fuel adder that compensates easily for around 5000-7000 ft elevation change when set up as directed. Been using them in bikes since 1989 with good results. Fact is two of the bikes have CV carbs, one has no jetting changes except adjusting the idle mix, even with a cut airbox lid, big bore, and open exhaust. From sea level at Daytona to the mountains of West Virginia - about a 5000 ft altitude change - and from 20 deg F to 95 deg F, no jetting issues. The 650 was lean to start, but the 250 was so lean it had to be jetted first. Where riders are doing around 135-140 range mains on the 250 I'm running a 125, the Dial-A-Jet makes up the difference.

Slide carbs outperform the CV with direct throttle to slide action, the reason riders use them for max performance. As early as the late 90s the hop ups for the KLX300R included replacing the CV on them with a flat slide and no serious off roader was without a slide carb (flat slides from the 90s on) until EFI.

Just sayin' If the money had been there when I got my 250 I'd have put the money for jetting into a flat slide pumper in a heart beat. A number of riders here have reinforced the benefits of the flat slide pumper, most saying it is the biggest performance enhancement short of a big bore and none have complained about altitude changes for the most part. It's just a really good option when considering about 1/3 the cost of the stronger performing carb has to be spent to bring the lower performing carb up to snuff. Why not just spring for the good stuff if the money can be spared?

 

Yer money ain't fer nuthin and yer chick's for free.. A pumper - especially Bill Blues' drop in / bolt on - certainly will give you more cowbell.. And who doesn't have a fever for more cowbell..? ..... we got to move these, refrigerators, we got to move these color.......