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Grouik 04-05-2011 02:27 PM

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.:norton

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


supershaft 04-05-2011 02:35 PM

Have you done any acclimation? I suspect how your carbs are breathing will be the least of your worries!

petefromberkeley 04-05-2011 03:30 PM

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.

Airhead Wrangler 04-05-2011 03:58 PM

I've had my R80 over 5000 meters without any trouble (other than seriously low on power). Just go do it.

mark1305 04-05-2011 04:29 PM

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.

icebox 04-05-2011 04:48 PM

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.

mark1305 04-05-2011 05:02 PM

Turbo Dual sports...
Hhmm... On that last wish, you might could find a decent Honda CX 500 Turbo (I think I got the model right), graft the right front end on it, play with the seat and subframe maybe, and end up with something close to what you wish for. Think in terms of smaller lighter and more tractable version of the Guzzi Quota.

Single track carver - not. But dual sport which keeps going when the pavement stops - possible.

Going back to the Dark Ages when I started riding, all motorcycles were dual sports. You took them anywhere they would fit, would climb, would hopefully get back home from.

There's potential out there sitting in barns, sheds, and the garages of anal retentives all over the place. :D

caponerd 04-05-2011 05:10 PM


Originally Posted by Grouik (Post 15594947)
A 16.000 feet pass with a 1982 R100:

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

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


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.

icebox 04-05-2011 05:15 PM

Don't want to swerve to far off course here, but OLD turbo's like the CX were not a low pressure turbo, they built their boost late in the RPM range and came on strong with a bang, also CX 650. I am old enough to remember riding Trump 650's almost EVERYWHERE, even hill climbs.
What makes a modern LOW pressure turbo work is electronics, knock sensors, oxygen and bar pressure sensors, They build boost and TORQUE way early in the combustion cycle, making for a small, lightweight, very tractable motor. VW was the first to push them on a large scale with the 1.8T, now they are every where, just google ecoboost.

Living at 6,700' with two airheads, that regulary go above ten, I don't think you will have any problems. The second post would be more important. Lots of people have trouble above 14,000. Vision gets wonky, headaches, strength and coordination. Never mind clear thought. Stop at the top and try to run!

Grider Pirate 04-05-2011 05:16 PM

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.....

mark1305 04-05-2011 05:31 PM

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.

elmontanero 04-05-2011 05:38 PM

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!

supershaft 04-05-2011 05:58 PM

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.

hardwaregrrl 04-05-2011 06:10 PM

I was nervous heading to CO, was only at 12,000 for a few days and running a 150 main. Just power loss, no biggie. Just had to plan a bit more carefully if I needed to pass.

supershaft 04-05-2011 06:15 PM

The atmosphere isn't linear. There is a Big Diff between 12 or 14 thousand feet and 16 thousand feet.

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