Stalling at altitude

During some recent mis-adventures in the High Atlas my R850GS starting stalling on idle at some where above 1500 -2000m. this meant i had to leave the choke on and then loose a lot of engine breaking. I would like to blame this for repeated slide offs in to the mud, but seriously proved quite dangerous on steep desents. The air filter had done about 4000m but wasn't too dirty and the problem rectifired itself once i dropped below 1500m. It did reoccur later at sea level but only when stuck in traffic jams after 8 hours riding. Everything was a bit hot.

I thought Fuel injection should have prevented this? Does anything need adjusting once you start getting this high.

I did have to run on leaded fuel on occasions. only put some where around 80-100litres in during the trip. Could this have effected the lamda sensor? causing the EFI to play up?

It is a concern as i was thinking of taking it to south america where the Andes can get much higher.

I'm trying to teach myself how to fix the bike ready to venture further afield so any advice and tips gratefully received.

A mate of mine ran his Adventure with a chip that was supposed to help with low octane fuel in S. America. It made no great difference in his opinion during the year he spent there. He went up very high, bike spluttered and banged (thin air, coupled with fuel less than Esso's finest) but it was all OK. 2000m (about the level for the start of decent skiing) is not that high, check that the injectors are balanced.

Your hot low level running was probably overheating causing vaporisation problems, more common on carb's but not unknown on injection engines. Relax, sit in the shade for half an hour.

Don't forget people have been taking petrol engined vehicles into the rougher ends of the world for years, virtualy since Mr Daimler built the first one. If they could do it in 1907 (no brakes, no roads!). http://www.carnet.co.uk/pekingparis/html/history.html You will be OK in 2006/7 Don't worry - just do it.

Hmmm,an odd one.

As you say,fuel injection should have adjusted itself to compensate.

I 've taken both of my R1100Gs`s to similar ( or maybe higher ) altitudes with no ill effects at all....one time it was in snow and ice,too.

I don`t think the leaded fuel you`ve used would cause the problem.

Maybe the airflow/air temperature sensor that sits inside the air filter is dodgy ??

( It`s mounted in the airbox lid )

http://www.horizonsunlimited.com/

Coupled with the book, can't remember its name (M/C riders hand book?) but will post when I get home. Useful bunch of girls and boys on the website.

i would have expected the lambda closed loop circuit to take care of most problems, maybe at that altitude it's outside it's operational parameters

1100/50 FI is pretty basic though. no air flow meter so i suspect the throttle position sensor is all the CPU relies on.

Is there a lambda sensor on your bike ?. If not, it may be the CO potentiometer under the seat that is set wrong. Some of the 1100s had no lambda sensor and had this 'pot' fitted instead. Do a search under 'CO potentiometer' and my username . I remeber posting some pics about this some time back.

Ferg