High altitude question for the jetting gods

I am going to Kennedy meadows (7500 to 9500) next week and was hoping to ask what I should expect. The bike is tuned for 2500 to 3500 and runs unbelievabl now. I have the octopus removed and rejetting for and running a 172 main, white bros. meg power, eseries pipe, zip ty fuel screw is installed (1 1/2 turns out). Will I have to change the main to something else, more, less? Or will the fuel screw be enough to tune it while im there? Thanks guys.

Drop your main 3 sizes, test ride and check fuel screw. Use your fuel screw setting to determine if you need to go to a different pilot, less than 3/4 turn in and you need a smaller pilot, more than 2 1/4 turns out and you need a larger pilot. I normally go up one pilot size, and it always seemed odd to me until I recently talked to a mechanic in Colorado. He said the reason for this is that at higher altitudes it is harder for the bike to make enough vacuum because the air is much less dense and the lower vacuum levels don't pull enough fuel at lower RPM. Hope this helps.


2 -3 sizes down on the main sounds about right. You may want to drop the needle 1 clip as well. You won't be on the main much at KM. I normally go down 1 size on the pilot as well. Never heard of going up on the pilot when going up in altitude. Seems a little strange to me.

Sorry, I completely forgot about the needle. I thought going up on the pilot was strange too, but it worked for me. Went along with what my fuel screw was telling me too. Go figure??


I just got back from riding high altitude. Changed my main to a 162. All you need is a 17mm wrench to unscrew the bowl cap and a 6-7mm (I use a 1/4") socket to unscrew your main and install a new one. JD Red needle on 4th pos., 1 1/2 turns out on fuel screw. You might get a burp here or there but it rips. Good luck.

keep the info coming thanks guys.

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