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Discussion Starter · #1 ·
Today, I went to the summit of Pike's Peak. 14,114 feet above sea level. It was quite cold and windy up there, but it was a great ride, and it really challenged my abilities when the wind buffeted me around on my light single cylinder.

I had lunch at the restaurant up there, for about an hour or so. When I tried to start my bike, the engine wouldn't turn over. Occasionally it would get some progress then stall. It took a few attempts, but I was able to start it by getting it going a bit and revving the dickens out of it a few times. I didn't dare let it go to idle speed until I was at a lower altitude. So far, no more problems.

Is this normal? Temperatures were pretty low, and the altitude is definitely up there. So O2 levels are down.

Just a quirk of a single, or do I have an issue needing to be fixed?

Sent from my Moto Z (2) using Tapatalk
 

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I hardly know anything about motorcycles or anything mechanical, so take this with a grain of salt. I was having this problem intermittently with my Kawasaki Eliminator 125, a single cylinder, even with the choke open and revving the throttle it sometimes wouldn't start or it would stall after just a bit. I haven't had that problem at all since discovering my battery cells were low on fluid. I have no idea if those two things are related.
 

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That's pretty high up - likely the altitude just messing with the fuel mixture. Many bikes will recommend modifications if they're continuously used at higher altitude (usually 5k feet or so - you're almost 3 times that!)
 

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...Is this normal? Temperatures were pretty low, and the altitude is definitely up there. So O2 levels are down.

Just a quirk of a single, or do I have an issue needing to be fixed?...
Not a quirk of a single and no, you don't have an issue that needs fixing.

While a modern fuel injected bike is running, oxygen sensors send data to the engine management system to control the air-fuel ratio. This feedback loop delivers the correct fueling regardless of air density changes from altitude and weather (temp and humidity).

Your bike is set-up to idle and run at a specific altitude and then it will adjust from there. Problem is it was not set up to idle and run at 14,000 feet. That's why you had trouble restarting it at the top of the mountain. Once running, the engine management system will adjust for the altitude and weather.
 

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Discussion Starter · #5 ·
Had the issue again even at lower altitude (9097 feet above sea level), though I did the same thing as before and gave the throttle a twist as the engine tried to turn over.

I live in Colorado on the Front Range of the Rocky Mountains, at my house it's over a mile above sea level. Anything I can do to prevent the issue if I go through mountains in the future?

Also, I did ride my bike to the top of Mt. Evans a few weeks back, and it's even higher than Pikes Peak. I didn't have an issue then and was probably parked about the same amount of time, though it was a bit warmer. Would temperature affect it?
 

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I think we can assume that if it was OK once you came back to a lower altitude, and that you are not going to climb such peaks again soon, you are good to go... no need to worry, just be happy!
 

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You didn't say whether your bike was carbureted or fuel injected. Mechanically carbureted need a high altitude kit usually 5,000+ feet and up, otherwise they run richer at elevation. This goes for cars, too. FI, starts in the program mode until warmed up sufficiently, then switches over to feedback mode. In other words, during feedback, your O2 sensor will determine whether you are at the right mixture, then will lean out the mixture to obtain the optimal stoichiometric mix. In program mode, it will run rich (unless certain adjustments are "programmed" for elevation).

At sea level, air pressure is 14.7 psia (pounds per square inch absolute). at 5,000 feet it is 12.2, at 8,000 - 11.0, at 10,000 - 10.1, at 14,000 - 8.7 psia. At 14,000, you have only have 59 percent of the available oxygen that you had at sea level.

14,000 ft. elevation is very high. I've not had any problems with my sea level manually carburetted bikes, the 1987 LS650 Suzuki Savage nor my 1971 Honda CB100 once I adjusted idle for location, Gallup NM 6,500 ft. The slide valve carburetors seem to handle changes in elevation relatively well. I've ridden the Savage and my 2001 Kawasaki ZG1200 Voyager XII up to 8,000 feet without problems.

You also have a loss in horsepower, roughly equivalent to the air pressure difference from sea level. Plus there will be a drop in cooling efficiency, hence why automatic transmission RV's and vehicles towing a trailer will overheat without a proper sized transmission oil cooler. (Seen that many times when living in Gallup.)

Glad you enjoyed your time at Pike's Peak, you were very fortunate that you didn't have any more problems with your bike that could have left you stranded.
 

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Discussion Starter · #8 ·
The bike is a modern fuel injected. It's brand new. Either way, I may take it in regardless, there's an annoying buzzing sound coming from the instrument cluster area between 6200 and 6800 rpm.

I figure I'd get a few annoyances with a 5000 bike made in India.

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