Jetting for St. Anthony
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  1. #1
    Junior Member ouo_250r's Avatar
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    Jetting for St. Anthony

    I’m out in Oregon and ride the coast and am (sea level) going to St. Anthony Idaho (5000-6000ft) in a few weeks . Not sure what to do about jetting . Any suggestions from guys that ride at 5000 ft ? All of our bikes are stock . Not sure of what jets to start with. Only going for a few days and don't want to spend the whole trip trying to rejet the carbs to get them to run or heaven forbid lean out and kill a cylinder .
    Last edited by ouo_250r; 03-27-2019 at 05:44 PM.

  2. #2
    Junior Member ouo_250r's Avatar
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    Just looking for a baseline of what sizes of jets to buy and have on hand.

  3. #3
    Junior Member ouo_250r's Avatar
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    also weather temps say 40-60 degrees and at sea level most days we ride are 60-75 so I know temp effects jetting too

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  5. #4
    Senior Member SandSlinger's Avatar
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    I'm not much help but when we went there from oregon in 99 we had to jet huge on my blaster, to get it to run halfway decent. 300ft to 5000ft is quite the change.
    Hopefully Carlos sees this and can give pointers he's pretty knowledgeable about jetting.
    Last edited by SandSlinger; 03-27-2019 at 07:41 PM.

  6. #5
    Senior Member acecarlos's Avatar
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    Quote Originally Posted by ouo_250r View Post
    I’m out in Oregon and ride the coast and am (sea level) going to St. Anthony Idaho (5000-6000ft) in a few weeks . Not sure what to do about jetting . Any suggestions from guys that ride at 5000 ft ? All of our bikes are stock . Not sure of what jets to start with. Only going for a few days and don't want to spend the whole trip trying to rejet the carbs to get them to run or heaven forbid lean out and kill a cylinder .
    Three changes going on for you:

    Higher altitude
    Lower Air temperatures
    Same dome size or engine compression

    At Higher altitudes you need to Lean your jetting out; 1 Main jet size smaller per 1500/2000 feet, lower needle 1 clip, decrease 1 size on pilot after +3000'
    Lower air temps require Richer jetting; increase 1 Main jet size for every -25F/30F, raise needle 1 clip, increase Pilot size +1 size at -30F or colder
    Best is to Increase compression when going from Sea Level to 4000'-6000' altitude, not practical for most, however; the correct approach for the best performance...-10% CC volume per +2000'

    In your case; start with what you have in place and be prepared to change Main, Pilot and Needle position as noted above.

    Carlos
    Last edited by acecarlos; 03-28-2019 at 10:30 AM.


 

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