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I plan on riding my 77 R100S from the west coast to Santa Fe, NM for a job in a month. I used to live there and love the excuse to travel back to New Mexico and eat Green Chile.

I'm starting to prepare my bike for the trip and I am beginning to wonder if there will be any issues with the standard 40mm carbs and the altitude?

Is there anything I should know or be prepared to do as I climb in elevation?

I regularly change elevations more than that with no problems, but it helps to lean the idle mixture a bit at higher altitudes. That said, I rode my R75/5 to the top of 13,900' Mauna Kea one time. It idled OK, but was a bit down on power. There's only 40% of the oxygen level at sea level up there.

If you have stock (CV) Bings, then you'll have no problem other than the aforementioned reduced power, and there's nothing that can be done about that without superchargers/turbochargers. The CV carb design compensates for altitude better than conventional slide carbs.

If you had slide carbs, you'd probably have to adjust your idle, and the bike would run a bit rich, but it would still work okay - 7000 ft. isn't that big a deal. I live at 6500 and have to cross passes from 7500 to 9000 feet, and then drop down to sea level, and my old slide carb bikes would just get a little funky up around 9000. From sea level to 7000 they were always fine.

This may be oversimplifying but when I spent time in the Rockies (on my '77 R100S) and I felt a let-down in power, I downshifted. Voila; instant pick-me-up. and no fooling around with jets.

Wookie

wookie wrote:This may be oversimplifying but when I spent time in the Rockies (on my '77 R100S) and I felt a let-down in power, I downshifted. Voila; instant pick-me-up. and no fooling around with jets.

Wookie

Yeah, that works on a 1000. Tim's talking about 14,000 ft. I'm not sure my R50/2 could have climbed a 1% grad in first gear at 14,000 ft.

Major Softie wrote:Yeah, that works on a 1000. Tim's talking about 14,000 ft. I'm not sure my R50/2 could have climbed a 1% grad in first gear at 14,000 ft.

I recall with amusement the phrase you coined some years ago relative to your R50/2 and it's acceleration. You called it "gathering momentum".

Ken

I live at 500 feet in Texas and spend most of my summers outside of Aspen at 7,000 - 9,000. My R65 loses a little bit of power, but runs fine. I have found that I save a lot of battery by changing my spark plugs every couple weeks. It runs a little rich and they blacken up pretty quickly.

This is good news. Thanks guys. Now I just have to worry about everything else that can go wonky. before the trip, I have work to do:
one caliper needs to be rebuilt,
slight generator light glow that I have tried many times to solve,
i hope to re-spline my final drive , etc...

Get the spline job done at Hansens. Two week turnaround. Brunos is currently buried in work and it can take many months...

We can actually do the splines here in Los Angeles. I'm not the one doing the work... so I can't claim my expertise but the guy I work with repaired a few already. Check out Oshmo.com for some of the services we can do.
I replaced wheel splines on the last bike I built.
We lighten flywheels in-house and we are working on some other services too....