high altitude jetting

2 replies to this topic
  • KAS

Posted July 20, 2008 - 10:12 AM


I'm currently running 48/165 on my '08. Most of my riding is sea level to around 3000 ft, and it works great.

However in a couple weeks I'll be going on vacation, and spending a week riding anywhere from 6000 to 8000 ft, very low humidity, temps in the 80s.

I'm thinking of going maybe to 45/160 or a 162 main.

Any thoughts? :thumbsup:

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  • William1

Posted July 20, 2008 - 11:36 AM


45/160, may even need to go as low as 38/145. You should also bring a few extra needles in thicker diameters to lean out everything in between idle and WOT.

Take a look at the Merge Racing site. They have a RAD (Relative Air Density) jetting calculator. You enter in current jetting, weather data and the chart then tells you what jetting is needed for other conditions.


  • grayracer513

Posted July 20, 2008 - 04:04 PM


Without considering anything but the change in altitude, the formula I have suggests 158/45.

The merge calculator looks good. Quite a few steps to get to it all, but very thorough. I'll have to fiddle with it some.

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