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Old 04-05-2011, 02:27 PM   #1
Grouik OP
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Altitude: 16.000 feet pass with a 1982 R100

A 16.000 feet pass with a 1982 R100:

I am on the leave for a week trip between Chile and Argentina.

We are going to ride the Passos Aguas Negra at 4.800 m (16.000 feet).

I guess the carbs needs a special tuning.
Could you please tell me what to do, a small picture would be welcome.

Thanks in advance

Pierre
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Old 04-05-2011, 02:35 PM   #2
supershaft
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Have you done any acclimation? I suspect how your carbs are breathing will be the least of your worries!
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Old 04-05-2011, 03:30 PM   #3
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I have gone that high with my R100 GS. I had little power but it made it OK. Usually, you are only up that high for a short time, so I don't think it's worth adjusting the carbs. Fine if you want to though or if you are going to be there for a while.
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Old 04-05-2011, 03:58 PM   #4
Airhead Wrangler
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I've had my R80 over 5000 meters without any trouble (other than seriously low on power). Just go do it.
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Old 04-05-2011, 04:29 PM   #5
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Yeah, if you have the Bing CV type carbs, they are pretty much self compensating for altitude within normal operating conditions. You will experience the loss of power, but no tuning can restore that power - in simplistic terms, it is a function of the lower atmospheric pressure and the resulting lower oxygen going into the motor as altitude increases.
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Old 04-05-2011, 04:48 PM   #6
icebox
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3%

Rule of thumb for naturally aspirated motors of ANY kind, gas, diesel, fuel injected or otherwise is 3% / 1000' of elevation. or at 6600' you lose 20% of your power. Which is why turbo motors are so popular in the Rocky Mtns. They are altitude compensating to 10,000', basically the turbo spools up faster with the thinner air to the set pressure of the waste gate.
Now if they just made a low pressure turbo 600 cc, high torque dual sport that weighed under 400 lbs.
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Old 04-07-2011, 07:48 AM   #7
Grouik OP
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Quote:
Originally Posted by mark1305 View Post
Yeah, if you have the Bing CV type carbs, they are pretty much self compensating for altitude within normal operating conditions. You will experience the loss of power, but no tuning can restore that power - in simplistic terms, it is a function of the lower atmospheric pressure and the resulting lower oxygen going into the motor as altitude increases.
Thank you for the explaination, easy, I will go
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Old 04-07-2011, 07:46 AM   #8
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Quote:
Originally Posted by Airhead Wrangler View Post
I've had my R80 over 5000 meters without any trouble (other than seriously low on power). Just go do it.
Ok , I will go !!!
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Old 04-05-2011, 05:10 PM   #9
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Quote:
Originally Posted by Grouik View Post
A 16.000 feet pass with a 1982 R100:

I am on the leave for a week trip between Chile and Argentina.

We are going to ride the Passos Aguas Negra at 4.800 m (16.000 feet).

I guess the carbs needs a special tuning.
Could you please tell me what to do, a small picture would be welcome.

Thanks in advance

Pierre
The vacuum control of the slide should help, but if it seems to be running rich, take the tops off your carbs, and lower the needles one notch for each 5000 feet, or until you get to the highest notch on each needle. The needles are moved by twisting them carefully, 90 degrees in either direction, then either pulling (to lower) or pushing (to raise).
There are (I'm pretty sure) 5 notches, and most bike have them in the middle notch.
Beyond that, it helps a bit to remove the air filter (or maybe not, if you're going to be on dirt roads!). Just remember to undo everything as you come down in elevation, or you'll be running very lean.
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Old 04-05-2011, 05:16 PM   #10
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Take oxygen for yourself. I fly a glider, and suffer splitting headaches for days after a flight when I spend more than a half hour above 12,000 feet without oxygen. I usually turn on the oxy at 11,000, especially if it's a good day and I'm climbing well.
Some people don't seem to have as much trouble as I do though.....
ymmv
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Old 04-05-2011, 05:31 PM   #11
mark1305
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Good points about personal oxygen needs. If you have never been that high - you don't know.

Where I grew up in GA a lot of my friends got pilots licenses before we graduated high school. One friend, a doctor's son, told me he couldn't go above 10,000 ft without oxygen or else he would completely pass out.

Something to be aware of, so that if you start feeling funny, you know to take it seriously.
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Old 04-05-2011, 05:38 PM   #12
elmontanero
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I must be extremely lucky or in good shape when I did it.. but 14,000 wasn't that big of a deal. Yeah... Walk then stop, walk then stop for a while, but then things just clicked over and no worry. This was after a 10 mile hike up the hill and all.

On a moto.. yeah I could see the bike straining... No worry on the headaches etc.

Have a great adventure and bring back pics!
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Old 04-07-2011, 08:07 AM   #13
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Quote:
Originally Posted by elmontanero View Post
I must be extremely lucky or in good shape when I did it.. but 14,000 wasn't that big of a deal. Yeah... Walk then stop, walk then stop for a while, but then things just clicked over and no worry. This was after a 10 mile hike up the hill and all.

On a moto.. yeah I could see the bike straining... No worry on the headaches etc.

Have a great adventure and bring back pics!

I did more or less the same hiking experience up to 14.500 feet a few year ago, not to much a problem.
I guess 16.000 feet just sitting on the bike will be OK as weel.

I will bring back and post some pictures on ADV forum.

Thank you all for your comments and advises.
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Old 04-05-2011, 05:58 PM   #14
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Hey pfb! It's me Billy over in SSF!

Being able to deal with altitude varies SO much. The absolute key is that you won' t be up there very long. If something happens and you are, you could be in serious trouble real fast and you WILL need help. Being above about 1400ft is enough to get even experienced climbers in trouble if they don't go through all the motions of their acclimation routine.

For the umpteenth time, CV carbs do not some how magically re-jet themselves for high altitude. The only thing they do in high altitude is the exact same thing they do at sea level and that is keeping the carb from getting more throttle than it really needs. That's it. Nothing else. It is really nothing that a well trained wrist couldn't do with a slide carb!

I would leave the needles alone. Too hard to get to and it involves re-syncing the carbs. IF I messed with it, I would screw the mixture screws in as I went up and change the mains. 125's work good above about 8000ft. I am guessing that 14000ft could use about 115's. They're are jetting charts that could check my own guessing if your interested.
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Old 04-05-2011, 06:17 PM   #15
fishkens
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Page 10 in the Bing manual goes into this in depth with a formula and chart for temp and elevation.

In short it says to compensate with the idle mix screw as SS says and then adj. the main jet.

Then it provides this example:

- Motor is well tuned in Galveston, TX (elev. 7') at 86 degrees; going to Denver, CO (elev. 5250') at 50 degrees would be roughly the same with a 145 main jet. If the temp was 86 degrees in Denver you'd go to a 142.

Much like the feedback already provided.
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