Air screw adjustment for altitude?

Hi,

Sorry if this has been covered before, my search did not turn up anything. I've gone from sea level to 5,000 feet and am wondering how many turns out on my airscrews I should go to compensate? Bike was feeling sluggish and I went out 1/2 turn and it's feeling better, but I'm wondering if there's a formula or standard amount? This is on KZ650 VM24 slide carbs.

Thanks.

I am no carb guru, that being said I do not believe fiddling with your air screw is going to change much. I used to have (and have another on order) a mikuni tuning manual from SUDCO that explains carbs pretty well. If memory serves me carbs are divided into circuits (idle, 1/4 throttle to 3/4, full throttle, etc) and each circuit is controlled by a certain part of the carb (air screw, pilot jet, main jet, main jet clips position)I would highly recommend the manual or something similar.

A VM24 carb needs to have the jet sizes decreased (all other things being equal) about 10 percent at 5K feet. If you had STOCK jetting, it isn't realistic to decrease the size of the #15 pilot jets but you can reclip your jet needle up one notch and decrease the size of the main jet. Typically about a #95 will be right if you are using a stock airbox. Reclip to 2nd slot (slots are counted top to bottom). That should perk your KZ up. Keep in mind that if you ride at sea level, it will not run all that great so if you plan at riding a lower elevations, you may wish to do a "compromise" rejet... clip to 3rd slot and go with a slightly larger main.

Hey, OK thanks the 10% is useful info. I'm on a roadtrip though -- not enough of a god to consider rejetting, or even re-clipping. Whatever I can do w/the airscrews will be it.

Anyway I'm now out 1 full turn. I did some 11,000 foot passes today and the bike lacks its usual pickup but it's getting the job done and my mileage isn't too bad. I just don't want to overdo it and run lean. (It's pretty hot here, even at 8-9,000.)

Hey, OK thanks the 10% is useful info. I'm on a roadtrip though -- not enough of a god to consider rejetting, or even re-clipping. Whatever I can do w/the airscrews will be it.

Anyway I'm now out 1 full turn. I did some 11,000 foot passes today and the bike lacks its usual pickup but it's getting the job done and my mileage isn't too bad. I just don't want to overdo it and run lean. (It's pretty hot here, even at 8-9,000.)