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Old 06-01-2012, 08:59 PM   #1
LandLeftBehind OP
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Altitude adjustment?

Ill be in the southwest this summer. At points ill be spending a few days in higher elevation (spending nights ~6000 ft in the Apache/Sitgreaves forest area). Im thinking about camping in Lincoln National forest for a night, which would be a dramatic 5000 ft rise (from ~3000 ft coming from Carlsbad, NM).

Do you guys think I'll need to bring smaller main jets? Could I get away with just resetting the mixture screw? Could I get away with doing nothing?
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Old 06-02-2012, 04:04 AM   #2
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Not to worry.......

I live at 6000ft, have stock jets & balance the carbs myself........

You may want to make a small adjustment once you get to elevation but your bike will do fine without adjusting.

my 2 cents
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Old 06-02-2012, 06:11 AM   #3
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What year/model of bike are you riding? Bings? Dellortos? I live in Las Cruces and regularly ride in the Cloudcroft and Ruidoso areas, up to 11,000 ft. elevation.
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Old 06-02-2012, 08:29 AM   #4
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year/model

'91 r100rt, stock bing 32s
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Old 06-02-2012, 08:30 AM   #5
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Originally Posted by brittrunyon View Post
Not to worry.......

I live at 6000ft, have stock jets & balance the carbs myself........

You may want to make a small adjustment once you get to elevation but your bike will do fine without adjusting.

my 2 cents
So may just one turn in on the mixture screw at elevation?
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Old 06-02-2012, 09:25 AM   #6
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One turn? Do you mean an entire 360*? How far out are you running those things? My bike is much older, a 1975 R90/6, but I set the mixture screws at 3/4 to start. I used to have them then a little richer than this after I finished but recently I changed to a 50 size idle jet, stock is 45, and think I'm going to end up a little leaner than 3/4. Not finished yet tho.

A small adjustment of the mixture screw is usually about 45* or less. These carbs are sensitive in my opinion.

The CV carbs are said to adjust for barometric pressure automatically.
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Old 06-02-2012, 12:12 PM   #7
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Quote:
Originally Posted by LandLeftBehind View Post
So may just one turn in on the mixture screw at elevation?
The mixture screw effects the idle mixture, not much effect on running down the highway when the carbs are operating on the main jet circuit. Several inmates have commented on the subject of altitude and Bings, and it has been addressed in other threads. It seems to be the consensus that the Bings tend to compensate very well for changing altitudes and there is no need to change jets. That having been said, it is my opinion that if one lived at or rode at a high elevation regularly then a change to smaller main jets can be tested. I am running smaller main jets and have dropped the needle down one notch, but I have Dellortos, not Bings.
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Old 06-02-2012, 12:17 PM   #8
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Originally Posted by disston View Post
One turn? Do you mean an entire 360*? How far out are you running those things? My bike is much older, a 1975 R90/6, but I set the mixture screws at 3/4 to start. I used to have them then a little richer than this after I finished but recently I changed to a 50 size idle jet, stock is 45, and think I'm going to end up a little leaner than 3/4. Not finished yet tho.

A small adjustment of the mixture screw is usually about 45* or less. These carbs are sensitive in my opinion.

The CV carbs are said to adjust for barometric pressure automatically.
When people refer to "turn" I always assumed 180 degrees. As I have never attempted tuning these particular carbs, its good to know that they are that sensitive.
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Old 06-02-2012, 12:36 PM   #9
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Originally Posted by LandLeftBehind View Post
When people refer to "turn" I always assumed 180 degrees. As I have never attempted tuning these particular carbs, its good to know that they are that sensitive.
Usually when we adjust the idle mixture screw it is done in 1/8 to 1/4 turn increments. Again, this controls idle circuit air/fuel ratio, which affects the engine at idle to part-throttle. I lived in Cloudcroft, NM around 9000 ft. elevation and re-jetted several carbs, used to like the "Dynojet" kits and followed their recommendations. Don't know if Dynojet makes a kit for Bings.
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Old 06-02-2012, 08:55 PM   #10
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Usually when we adjust the idle mixture screw it is done in 1/8 to 1/4 turn increments. Again, this controls idle circuit air/fuel ratio, which affects the engine at idle to part-throttle. I lived in Cloudcroft, NM around 9000 ft. elevation and re-jetted several carbs, used to like the "Dynojet" kits and followed their recommendations. Don't know if Dynojet makes a kit for Bings.
Neat! If all goes according to plan Ill be passing right through there. Any recommendations where to camp?
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Old 06-02-2012, 09:28 PM   #11
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You won't need to rejet those carbs. They are jetted about perfect from the factory excepting just a tad too lean needle jet. That isn't going to hurt you at altitude. Crawdds had to rejet his Dell's because BMW jets them way too rich at sea level let alone any altitude. Like crawdds said with those Dell's, they are especially too rich on the mains. It might help to lean your mixture screws (in) a little. Especially to help start up. How much? That can vary widely from carb to carb let alone bike to bike. It all depends on how EACH carb's mixture screw tunes. How far is EACH carbs rich and lean stumble points from each other? It it one full turn on one carb and one half turn on the other. They very often are different. If so, for instance, turn the one screw in one quarter turn and the other screw in about an hour and a half. That will effect each carb's mixture the same versus treating that screw like all carbs are the same. They are not. That is the whole reason that screw is there to start with. Good luck!

supershaft screwed with this post 06-02-2012 at 09:42 PM
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Old 06-02-2012, 11:07 PM   #12
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Unless you're now running richer than stock jets, you'll be fine at 6,000 ft with stock jetting.
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Old 06-03-2012, 06:51 AM   #13
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I rode through the Rockies, Colorado to Banff last summer and never rejetted. I only noticed the power loss when passing going up passes, but nothing crazy.
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Old 06-03-2012, 07:34 AM   #14
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Any recommendations where to camp?
Where to start? There are so many great roads to ride and beautiful places to see. Must ride roads... 130, 244, 130, 24, 6563, Ski Run Road up to Ski Apache - way too many to list. Ride south on road 6563, turn east on 164, camp at Bluff Springs! Check with Forrest Service first, camp sites/trails/roads may be closed because of drought.
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Old 06-03-2012, 07:37 AM   #15
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I've rode my GS through all the areas you plan to visit, and many much higher. Stock jetting ...

I wouldn't touch a thing. You will lose some power at elevation, but that's just the way it goes.
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