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Author Topic: rejetting for elevation  (Read 228 times)

rural earl

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rejetting for elevation
« on: July 16, 2013, 10:36:50 PM »
I just have to ask this.  Suppose I get an iron-barrel Bullet with the stock carb.  If I get the jets right at my present home elevation (<100 feet above sea level), will I have to rejet when I ride to areas near 5000 feet?  How many times?  I guess the bike will run richer and richer until it quits as I climb higher and higher.  I'm just wondering how much leeway I can expect, since my longer rides usually mean major elevation swings.  Seems inconvenient, but if that's what it takes, I'll bring the Mikuni calculator and a bunch of jets along.

High On Octane

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Re: rejetting for elevation
« Reply #1 on: July 16, 2013, 10:51:44 PM »
The general rule of thumb is 10% reduction in the main jet for every 5000'.  I live in Denver and have my bike tuned for mile high.  I'll let you know what happens when I climb to 10,000'+.  I'm hoping I can get enough adjustment out of the air screw without having to rejet.

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Scottie J
Denver, CO

1958 Enfield/Indian Trailblazer

barenekd

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Re: rejetting for elevation
« Reply #2 on: July 16, 2013, 11:32:54 PM »
I jet size every 2500 feet is usually the call. However the Indians on their epic road tours up to 17,000 feet usually don't bother changing the sea level jets until about 12,000. If yu jet your bike for 5000', which you should, 10,000 will not be an issue.
It's the racers looking for ultimate performance who change jets at tehsoe samell increments. Street riders need not worry!
I lost a scrambles race in Laramie, Wyoming  (7500') once because I didn't rejet my bike from the sea level setting. The other guy just had a hair of power on the straights, but I was beating him the rest for the way around. Just never could quite get around him! I just need that smidgen more power. I never did that again!
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rural earl

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Re: rejetting for elevation
« Reply #3 on: July 17, 2013, 12:19:14 AM »
Jetting for 5000 feet makes sense...that way you can go up or down a ways without leaving the sweet spot.  One reason I asked about this was the way my Honda Nighthawk 250 ran well at altitude but couldn't hang on the freeway at sea level.  It was too lean, I guess, with the stock non-adjustable carb, and just ran better up high.