Go Back   Horizons Unlimited - The HUBB > Technical, Bike forums > BMW Tech
BMW Tech BMW Tech Forum - For Questions specific and of interest to BMW riders only.
Photo by Hendi Kaf, in Cambodia

I haven't been everywhere...
but it's on my list!


Photo by Hendi Kaf,
in Cambodia



Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 22 Oct 2007
Contributing Member
Veteran HUBBer
 
Join Date: Feb 2005
Location: Australia
Posts: 131
R100GS at Altitude

Greetings All

Has anyone had any experience with running A R100GS at altitude? We are heading down to SA and even now while we are travelling in the US at around 6000 ft the idle needs to be upped. (I never appreciated how flat Australia is)

Did you change jets? What sort of adjustment was needed? Tweaking carbs is a skill I haven't had a lot of experience with.

I did a search of HU and there is one other post relating to this, just looking for extra info.

Thanks for your help

Ian
__________________
Always have plan B, and maybe plan C
www.travelswithkitty.com
Reply With Quote
  #2  
Old 22 Oct 2007
Redboots's Avatar
Registered Users
Veteran HUBBer
 
Join Date: Feb 2006
Location: On the border - NE FR
Posts: 865
Hight

Quote:
Originally Posted by IanJ View Post
Greetings All

Has anyone had any experience with running A R100GS at altitude?
Hi Ian,

rode through western China and down through the Pamirs, Karakorams and Himalayas over 5 week period.
Hight was up to 4600 metres and the only problem was the idle went to rats.
And a bit down on power but that's no big deal.
I did not adjust anything. I didn't feel the need to. How often do you leave the bike on idle?

Cheers,
John
__________________
Nostradamus Ate My Hamster
Reply With Quote
  #3  
Old 22 Oct 2007
AliBaba's Avatar
Registered Users
Veteran HUBBer
 
Join Date: Apr 2001
Location: Norway
Posts: 1,379
As you know you will loose some power and your idle speed drops. For me the power has never been a real issue but at 10.000 feet it is very noticeable. It might help to drop the needle one notch but I have never bothered.

I usually adjust my idling speed, but nothing else.
Reply With Quote
  #4  
Old 22 Oct 2007
beddhist's Avatar
Contributing Member
Veteran HUBBer
 
Join Date: Sep 2003
Location: Whangarei, NZ
Posts: 2,214
We are in Tibet and there are a couple of these bikes with me. They didn't change anything. Lots of passes 4500 - 5200 m high. No problems.
__________________
Cheers,
Peter.

Europe to NZ 2006-10
Reply With Quote
  #5  
Old 22 Oct 2007
Registered Users
Veteran HUBBer
 
Join Date: Nov 2003
Location: Berkeley, CA USA
Posts: 312
Quote:
Originally Posted by Redboots View Post
Hi Ian,

rode through western China and down through the Pamirs, Karakorams and Himalayas over 5 week period.
Hight was up to 4600 metres and the only problem was the idle went to rats.
And a bit down on power but that's no big deal.
I did not adjust anything. I didn't feel the need to. How often do you leave the bike on idle?

Cheers,
John
Yep, it does not run very well at altitude, but I never did anything about it. No problem.
Reply With Quote
  #6  
Old 24 Oct 2007
Contributing Member
Veteran HUBBer
 
Join Date: Feb 2005
Location: Australia
Posts: 131
Thanks for the replies,

I will need to up the idle as it just stalls immediately when I stop which is a pain while trying to manoeuvre at low speed two up and fully loaded but that would seem to be all.

I did check the plugs today and they are still in good nick, no carbon build up.

Ian J
__________________
Always have plan B, and maybe plan C
www.travelswithkitty.com
Reply With Quote
  #7  
Old 24 Oct 2007
seanh's Avatar
Gold Member
Veteran HUBBer
 
Join Date: May 2004
Location: Melbourne, Victoria, Australia
Posts: 301
I took my R65 over 5600 metres in Northern India, same experience had to adjust the idle but that's it. You can put in smaller jets and drop the needles, but if you have enough power to get up, there's no need really. As the altitude changes constantly in mountainous areas, you'll never get it exactly right anyway. Also, if you neglect to change it back at lower altitude, you will be running lean, which could cause some problems.
Sean
Reply With Quote
  #8  
Old 24 Oct 2007
Registered Users
New on the HUBB
 
Join Date: Jan 2007
Location: split-croatia
Posts: 7
At stella alpina meeting last summer my 100gspd also stalled idling, but I used my throttle screw as a help to maintain idle rpm. No other problems, at sea level everything was ok again.

Cheers, Stipe
Reply With Quote
  #9  
Old 26 Oct 2007
Registered Users
Veteran HUBBer
 
Join Date: Jun 2005
Location: Cape Town / South Africa
Posts: 207
Dropping the needle one notch will only have an effect at over 4000rpm. If you want to lean out the idle mixture for better idling you will need to adjust the screw directly in front of the float bowl. You can reach this from the bottom where you will find two screws, the small one is plugging a hole for connecting a vacuum gauge to help with balancing the carbs, and the larger one recessed in a small tower is the idle mixture screw. The idle mixture screw is normally set at a specific setting for different models but by turning it out a half turn or so you will supply more air to lean out the over rich idle mixture.

To make an adjustment to the idling speed is real simple. You need a flat screw driver an adjust the two hex screws with screwdriver slots in them directly in front of the carburettor cover from above.
If you are worried about the balance between the two carbs make a note of the amount you turn the screw in. For example start by making on quarter turn on each side and if that is not enough do another quarter turn till you are happy it idles fine. Remember to add the quarter turns and make a note to reset when at lower altitude again.(this technique can be used for both idle speed and idle mixture adjustments.)

IMPORTANT: do this once the bike is at the normal operating temperature. This will take about 10 minutes of driving under normal load.

As one member commented though you don't spend lots of time at idle but mostly around the 4000rpm mark. Dropping the nozzle needle one notch will have a dramatic effect on the performance and fuel consumption. The loss of power is partly on account of the smaller amount of air that mixes with the fuel, and as we know that to burn the fuel well we need lots of air. The problem is now compounded because the over rich mixture will cause the fuel to burn slower resulting in a loss of power.
Leaning out the mixture by reducing the amount of fuel supplied (this is the opposite from adjusting the idle mixture where you are increasing the amount of air to lean out the mixture.) will result in better burning of the mixture.
To drop the needle you do not need to remove the carbs. With the cables attached remove both the springs for the throttle and choke cables behind the carbs. You should be able to move both throttle and choke levers in an upward position to remove the cable nipples from the mechanism. Loosen the two screws on the cover and you can remove the cover with both cables attached.
Pull out the piston and by gripping the needle firmly turn it one quarter turn and pull on the needle. It should drop down about one millimeter and clip into the next notch firmly.
Refit the lot and remember to change the needle position back when you are at lower altitudes again.
The most common position is the third notch from the top and on some models the fourth, you will have to get the specs for your particular model though and remember that BMW changed the size of the jets and needles from some year models so it will differ on some year models as well.
Reply With Quote
  #10  
Old 30 Oct 2007
Contributing Member
Veteran HUBBer
 
Join Date: Feb 2005
Location: Australia
Posts: 131
Thanks for that,

I'll digest all that and have a gentle tweak at a later stage,

Ian
__________________
Always have plan B, and maybe plan C
www.travelswithkitty.com
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 Registered Users and/or Members and 1 guests)
 

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
XT600e Altitude Sickness dionysos Yamaha Tech 11 12 Sep 2007 19:30
´88 R100GS and Bolivian Fuel & Altitude? nickc BMW Tech 3 2 May 2005 09:49
R100GS ve8nc BMW Tech 3 29 Oct 2003 03:34
Automatic carb adjustment for altitude - MkII 3AJ Barry Johnson Yamaha Tech 1 2 Apr 2003 01:57

 
 

Announcements

Thinking about traveling? Not sure about the whole thing? Watch the HU Achievable Dream Video Trailers and then get ALL the information you need to get inspired and learn how to travel anywhere in the world!

Have YOU ever wondered who has ridden around the world? We did too - and now here's the list of Circumnavigators!
Check it out now
, and add your information if we didn't find you.

Next HU Eventscalendar

25 years of HU Events
Be sure to join us for this huge milestone!

ALL Dates subject to change.

2025 Confirmed Events:

Virginia: April 24-27
Queensland is back! May 2-5
Ecuador June 13-15
Germany Summer: May 29-June 1
CanWest: July 10-13
Switzerland: Date TBC
Ecuador: Date TBC
Romania: Date TBC
Austria: Sept. 11-14
California: September 18-21
France: September 19-21
Germany Autumn: Oct 30-Nov 2

Add yourself to the Updates List for each event!

Questions about an event? Ask here

See all event details

 
World's most listened to Adventure Motorbike Show!
Check the RAW segments; Grant, your HU host is on every month!
Episodes below to listen to while you, err, pretend to do something or other...

Adventurous Bikers – We've got all your Hygiene & Protection needs SORTED! Powdered Hair & Body Wash, Moisturising Cream Insect Repellent, and Moisturising Cream Sunscreen SPF50. ESSENTIAL | CONVENIENT | FUNCTIONAL.

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

"Ultimate global guide for red-blooded bikers planning overseas exploration. Covers choice & preparation of best bike, shipping overseas, baggage design, riding techniques, travel health, visas, documentation, safety and useful addresses." Recommended. (Grant)



Ripcord Rescue Travel Insurance.

Ripcord Rescue Travel Insurance™ combines into a single integrated program the best evacuation and rescue with the premier travel insurance coverages designed for adventurers.

Led by special operations veterans, Stanford Medicine affiliated physicians, paramedics and other travel experts, Ripcord is perfect for adventure seekers, climbers, skiers, sports enthusiasts, hunters, international travelers, humanitarian efforts, expeditions and more.

Ripcord travel protection is now available for ALL nationalities, and travel is covered on motorcycles of all sizes!


 

What others say about HU...

"This site is the BIBLE for international bike travelers." Greg, Australia

"Thank you! The web site, The travels, The insight, The inspiration, Everything, just thanks." Colin, UK

"My friend and I are planning a trip from Singapore to England... We found (the HU) site invaluable as an aid to planning and have based a lot of our purchases (bikes, riding gear, etc.) on what we have learned from this site." Phil, Australia

"I for one always had an adventurous spirit, but you and Susan lit the fire for my trip and I'll be forever grateful for what you two do to inspire others to just do it." Brent, USA

"Your website is a mecca of valuable information and the (video) series is informative, entertaining, and inspiring!" Jennifer, Canada

"Your worldwide organisation and events are the Go To places to for all serious touring and aspiring touring bikers." Trevor, South Africa

"This is the answer to all my questions." Haydn, Australia

"Keep going the excellent work you are doing for Horizons Unlimited - I love it!" Thomas, Germany

Lots more comments here!



Five books by Graham Field!

Diaries of a compulsive traveller
by Graham Field
Book, eBook, Audiobook

"A compelling, honest, inspiring and entertaining writing style with a built-in feel-good factor" Get them NOW from the authors' website and Amazon.com, Amazon.ca, Amazon.co.uk.



Back Road Map Books and Backroad GPS Maps for all of Canada - a must have!

New to Horizons Unlimited?

New to motorcycle travelling? New to the HU site? Confused? Too many options? It's really very simple - just 4 easy steps!

Horizons Unlimited was founded in 1997 by Grant and Susan Johnson following their journey around the world on a BMW R80G/S.

Susan and Grant Johnson Read more about Grant & Susan's story

Membership - help keep us going!

Horizons Unlimited is not a big multi-national company, just two people who love motorcycle travel and have grown what started as a hobby in 1997 into a full time job (usually 8-10 hours per day and 7 days a week) and a labour of love. To keep it going and a roof over our heads, we run events all over the world with the help of volunteers; we sell inspirational and informative DVDs; we have a few selected advertisers; and we make a small amount from memberships.

You don't have to be a Member to come to an HU meeting, access the website, or ask questions on the HUBB. What you get for your membership contribution is our sincere gratitude, good karma and knowing that you're helping to keep the motorcycle travel dream alive. Contributing Members and Gold Members do get additional features on the HUBB. Here's a list of all the Member benefits on the HUBB.




All times are GMT +1. The time now is 00:56.