Last week I finally got the jetting dialed in on my Wolverine for home which is at 831 feet. I went to one of my ridding areas today that varies from 1700-1950 feet. It ran like crap from 1/4 to 3/4 throttle. Idling and full throttle were fine. Does a higher altitude cause you to run richer or leaner? I have my needle set in the fourth notch from the top, second from the bottom. So I would think my needle is set on the rich side. If altitude make you run richer, then I need to move the needle clip to the middle notch or maybe even the next one up. Am I right? The reason I run it in the fourth notch from the top is because it didn't pull hard in the mid range when I had it set in the middle notch. Moving it down a notch got rid of my flat spot at home. Now that I am home, I took the quad out and it runs great again. So, do I need to go richer or leaner when I ride in higher altitudes? Thanks.

 

An increase in altitude will cause your engine to run richer. However a change in altitude that you described as being 1200 feet, will not cause a noticable difference in the way an engine runs, unless it is already in a borderline condition. If it were me I would go up one more on the main, lowere the needle 1 and reset the idle mixture, and if needed go up one on the pilot. What has happened is that you are having to make up for a main jet that is slightly too small with an increase in midrange fuel. If you have the carb correctly jetted for 800 feet then going to 2000 feet will not hurt your performance. Generally an increase of 4000 to 5000 feet will require a jet change, but what you described will not, if everything is correct.
Ron