Im running a 175 main and Im at approximately 1500ft give or take. Taking a trip to colorado in july and the elevation is 7500+. I tried last year to just take off the airbox lid and it was better but i would like to get a good idea of a jet that would be adequate for the elevation. Thanks

 

For that elevation I would go to a 160-165

 

What mods do you have?

 

K&N and a muffler tip...

 

Main Jet Corrections, rules of thumb:

Altitude correction - drop one 5.0 increment (two jets-155 to 150) for every increase of 3000'

Temperature correction - increase one increment of 5.0 (two jets-150 to 155) for every 30 deg. drop

Humidity correction - increase one increment of 5.0 (two jets-150 to 155) for every 30% drop

Needle Adjustment - Example - If running in the 3rd notch from top, sea level,
When running above 5000ft - lower to 2nd notch or try 85 octane

OMR

 

On the topic of jetting I have an extra stock carb around that I am starting to play around with. I remember some time back Mr HP and Randall recommended taking the main jet way down to a 150 (mikuni jet) even at sea level. Has anyone tried this and if so what were your results? I image you would have to run the needle pretty rich (4th or 5th notch from the top) to get away with this small of a main.

 

To run a 150 mikuni main:
Slightly reduce the size of inlet tubes and this increases velocity and builds huge pressure in the airbox. Makes for great bottom and mid. Takes away about 2 horsepower on top. This is what we did 5 years ago.

Today I am running between a 150 and 155 mikuni/ 160-165 DJ.
Airjet reduction builds more carb pressure and Stock carb mods.
Results: Great bottom and top.

OMR

 

thanks, what needle position are you using with this setup? Also what type/size of material do you recommend for decreasing the inlet tube size? Any pics of your airbox setup? For the past two years I have been running with no tubes and it runs pretty good.