Elevation changes?
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Cruiser
Joined: Aug 2012
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From: Keno
Elevation changes?
I'm starting a ~4,000 mile trip in a couple weeks. It'll have me going from home near sea level, to routinely in 5-7k elevation and briefly as high as 9k. Bike is an 01 RK with the following build: 95" SE pistons, .030 HG, Andrews 21 cams, Rinehart 2:1, Ness Big Sucker. Carb is stock except for the Sportster needle.
Bike runs like a top around town, no issues. Should I consider bringing a handful of jets along?
Bike runs like a top around town, no issues. Should I consider bringing a handful of jets along?
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,143
Likes: 11,212
From: San Diego, CA
I think if you're dialed in with your tune, you won't see any problems at the altitudes you're going.
I rode two different shovels from San Diego to Yosemite, via Tioga Pass (10K'), about 6 or 7 times. I never had a problem.
We had one guy out of our group, who had trouble going through the pass. He admitted that his bike was running rich at sea level.
Enjoy the trip.....
I rode two different shovels from San Diego to Yosemite, via Tioga Pass (10K'), about 6 or 7 times. I never had a problem.
We had one guy out of our group, who had trouble going through the pass. He admitted that his bike was running rich at sea level.
Enjoy the trip.....
Stellar HDF Member
Joined: Jul 2009
Posts: 2,011
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From: Albuquerque New Mexico
Good question, my buddies 02 RK with a 106 S&S blubbers and gets bad gas mileage at higher elevation. I rode the highest paved road on the continent, Mt Evans at 14270, and lowest in the US, Death Valley at - 280 in the last few months and it ran flawlessly. But that is with EFI
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
OP you'll be fine.
the Keihin CV ( Constant Velocity) carb self adjusts for changes in air density whether temperature or altitude...or weather.
The size of the hole is determined by the air rushing through it and pushing the slide up...thick air= big hole/ thin air= small hole.
the needle is held by the slide...the farther the slide rises ( big hole) the more fuel is added to the air...if the slide doesn;t rise much ( thin air/small hole) less gas is added.
My evos regularly run from 1200' to 8000' with some 11's too.
My 80" evo will leave mikuni'd and S&S'd big motor bikes way behind- those carbs are fixed.
enjoy your trip
The CV carb often outperforms the M&M and Delphi EFI measured for Power, MPG and emissions.
Mike
the Keihin CV ( Constant Velocity) carb self adjusts for changes in air density whether temperature or altitude...or weather.
The size of the hole is determined by the air rushing through it and pushing the slide up...thick air= big hole/ thin air= small hole.
the needle is held by the slide...the farther the slide rises ( big hole) the more fuel is added to the air...if the slide doesn;t rise much ( thin air/small hole) less gas is added.
My evos regularly run from 1200' to 8000' with some 11's too.
My 80" evo will leave mikuni'd and S&S'd big motor bikes way behind- those carbs are fixed.
enjoy your trip
The CV carb often outperforms the M&M and Delphi EFI measured for Power, MPG and emissions.
Mike
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Cruiser
Joined: Aug 2012
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From: Keno
Thanks guys. Great point MK - I know how a CV carb works but I had completely forgotten that it can account for changes in air density as well. I'm feeling pretty confident it'll be good now.
Should be a great trip - Milwaukee area through Missouri, Oklahoma, and north Texas to Upper New Mexico to Flagstaff, then up to Moab, then down through mid Colorado to Colorado Springs, home through KC and Iowa. First two and last two days will be pretty boring "just get there" days, but we're in AZ for 4 days, UT for 2, and CO for two.
Should be a great trip - Milwaukee area through Missouri, Oklahoma, and north Texas to Upper New Mexico to Flagstaff, then up to Moab, then down through mid Colorado to Colorado Springs, home through KC and Iowa. First two and last two days will be pretty boring "just get there" days, but we're in AZ for 4 days, UT for 2, and CO for two.
Last edited by Nilla; Aug 27, 2014 at 07:23 PM.
Extreme HDF Member
Joined: Sep 2010
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From: Phoenix '53, '88, '09 Big Twins
make sure you go through Monument Valley:
I often stay at the San Juan Inn in Mexican Hat, from there you can take #261 and go up the Dugway ( gravel) toward Natural Bridges Monument...swing East toward Blanding and N to Moab.
Dugway:
If you are doing the GC, Best Western does a hOG discount and is probably the best food in town...bowling alley in the basement level
Expect temps up there to be in the 40's/50's at night.
Elk are always a concern late aft into night in any wooded areas- their eyes do not reflect ( like deer) all you'll see is a tawny patch on teh rear- loud pipes do not scare them...I am usually done riding by 5 ish.
Central CO is good, very good, just came back.
Until mid-Sept we are in Monsoon season watch for late afternoon storms coming from the SE. These usually blow through fast and violent. Just wait it out
mike
I often stay at the San Juan Inn in Mexican Hat, from there you can take #261 and go up the Dugway ( gravel) toward Natural Bridges Monument...swing East toward Blanding and N to Moab.
Dugway:
If you are doing the GC, Best Western does a hOG discount and is probably the best food in town...bowling alley in the basement level
Expect temps up there to be in the 40's/50's at night.
Elk are always a concern late aft into night in any wooded areas- their eyes do not reflect ( like deer) all you'll see is a tawny patch on teh rear- loud pipes do not scare them...I am usually done riding by 5 ish.
Central CO is good, very good, just came back.
Until mid-Sept we are in Monsoon season watch for late afternoon storms coming from the SE. These usually blow through fast and violent. Just wait it out
mike
Last edited by mkguitar; Aug 27, 2014 at 07:57 PM.
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Stellar HDF Member
Joined: Dec 2005
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From: Milton, Delaware
I agree with MKGuitar, if you want a fun ride make sure to ride 261 and take the Moki Dugway.
Monument Valley is also a cool place. We stayed at 'The View' lodge in the reservation.
Monument Valley is also a cool place. We stayed at 'The View' lodge in the reservation.
Last edited by Deucedog; Aug 27, 2014 at 08:20 PM.
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Seasoned HDF Member
Joined: Sep 2008
Posts: 14,143
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From: San Diego, CA
Damn... you guys are killing me about the Utah leg....!!
When I went through Utah in 2012, the temps were over 100 degrees.... It was like driving a car with the heater on full...
I didn't stop or deviate from the main route all through Utah. I knew I would regret it...
But when I packed my bike to leave Moab at 0700, it was already 90 degrees....
Although I went by Monument Valley, it was at 75MPH and the only pics are in my head.
I'll have to go through there again for sure....
When I went through Utah in 2012, the temps were over 100 degrees.... It was like driving a car with the heater on full...
I didn't stop or deviate from the main route all through Utah. I knew I would regret it...
But when I packed my bike to leave Moab at 0700, it was already 90 degrees....
Although I went by Monument Valley, it was at 75MPH and the only pics are in my head.
I'll have to go through there again for sure....
HDF Community Team
Joined: Nov 2012
Posts: 6,189
Likes: 2,419
From: USA
My experiences with CV carburetors in general is that they handle altitude changes just fine. The thinner air will reduce power and gas mileage and create an increasing throttle snap bog, but by no means render the machine undriveable/rideable. I'd have to usually get upwards of 12000 feet to start running into appreciable driveability/rideability changes.