Rejetting for altitude

[mcrenshaw]

I'm planning on making a ride through New Mexico in a couple of weeks on my '93 R100GS. Being a North Texas flatlander the bike is jetted for the 700 ft altitude here. Since I'll be riding between 5000 to 8000 ft in New Mexico is rejetting recommended? If so, what do I use?

 

[20774]

The Bing carbs do a good job of self-adjusting for altitude. I wouldn't change the settings if you were only going to be there a short while or passing through. You might have to adjust the idle speed, but you can do that easily and evenly...then set it back to exact number of turns at a later time.

 

[Rinty]

I ran my airhead up to 11,000 feet, in the Beartooth Pass - no problems.

IIRC, some guys have operated them at incredible altitudes, in the Andes.

 

[RonKMiller]

On Monday I took my '79 R80 from 2600 feet (where I live) to 9,150 feet at the top of Mt. Lemon - in 35 miles! Temperature ranged from 71F at the top to 97F on the way back to my house. Good thing it only takes 15 minutes from the base of the mountain to my house. I try to time traffic lights so that I'm not idling.

The only difference I noted was a a loss of power and of course the idle dropped off - which I didn't bother adjusting. Other than that it was business as usual - and this with the flat top CV carbs.

It's going to be 105F this weekend in Tucson - and I can't wait to go riding! (uphill and EARLY) Bonus points: the restaurant at the top has about 10 different kinds of PIE.

 

[RonKMiller]

I'm planning on making a ride through New Mexico in a couple of weeks on my '93 R100GS. Being a North Texas flatlander the bike is jetted for the 700 ft altitude here. Since I'll be riding between 5000 to 8000 ft in New Mexico is rejetting recommended? If so, what do I use?

1. Make SURE you ride Highway 191 (The old route 666 - the "Devil's Highway") on the AZ - NM border while you're there. You can make a loop out of it. Even though it's only about 90 miles long plan on half a day...

This is one of the absolute best mc roads in North America. Damn, I just gave away a huge secret.

2. Take the Taos High Road.

3. Plan to spend some time in Los Alamos - some cool "nucular" museums and a bunch of nerds to go with them.

4. Be "vewwwy kehhfull" in ABQ. LOTS of gang bangers and druggies. I don't know why but my spidey sense is always on full alert whenever I'm there. Just plain creepy. Avoid it if at all possible. Kind of like South Tucson.

 

[page5240]

You say the bike is "jetted for 700 feet"...are you saying that you have had someone actually rejet your GS or are you assuming that it was set up for your altitude?

My guess is your bike is as it came from the factory, bone stock,....as was my 88 R100GS. I lived in New Mexico when I bought it in 1988 and it ran fine at 5000 feet where I lived (Albuquerque) and all through the mountains of New Mexico and Colorado. I rode this bike in Alaska, and all up and down the east coast and never had a problem with "jetting", you probably won't either.

I don't agree with the Ron's assessment of danger in Albuquerque, just stay away from the South Valley and you'll be fine. Every major city in the country has a "bad" part of town, in the Albuquerque area it's the South Valley....west of I 25 and south of I 40.

However if you feel like living on the edge take the Gibson exit off of I 25 and go west to Rio Grande Blvd then south a couple of blocks to Grandma's K and I diner. Order the Travis, you won't be disappointed...ride to eat, eat to ride.....

Long Distance Rider

 

[RonKMiller]

You say the bike is "jetted for 700 feet"...are you saying that you have had someone actually rejet your GS or are you assuming that it was set up for your altitude?

My guess is your bike is as it came from the factory, bone stock,....as was my 88 R100GS. I lived in New Mexico when I bought it in 1988 and it ran fine at 5000 feet where I lived (Albuquerque) and all through the mountains of New Mexico and Colorado. I rode this bike in Alaska, and all up and down the east coast and never had a problem with "jetting", you probably won't either.

I don't agree with the Ron's assessment of danger in Albuquerque, just stay away from the South Valley and you'll be fine. Every major city in the country has a "bad" part of town, in the Albuquerque area it's the South Valley....west of I 25 and south of I 40.

However if you feel like living on the edge take the Gibson exit off of I 25 and go west to Rio Grande Blvd then south a couple of blocks to Grandma's K and I diner. Order the Travis, you won't be disappointed...ride to eat, eat to ride.....

Long Distance Rider

Good point - you always need to be in condition "yellow" when in big cities. Although I would go to South Tucson during the day it ain't no place for a BMW drivin' white boy at night.

Perhaps I could pick on Camden, NJ instead.

Anybody here representin' Camden?

 

[mcrenshaw]

Re the stock set up on my bike. It's a 93 R100GS that is still bone stock. The bike came out of the dealer at Baton Rouge, LA. I'm the second owner. Runs and idles great so it sounds like I don't need to make any changes.

I got my very first bike in Albuquerque when I was stationed there from '70-72. Back in the day Wyoming Blvd was the last street to the east and it was open mesa all the way to Sandia Peak. Some great riding at the time but it's all development now. I doubt very much that we'll be staying over in ABQ.

My wife has never been to Carlsbad Caverns and wants to see them (she loves bats) so we stop over there then head down to the Guadalupe Mountains and make a loop west up to Dell City to Cloudcroft/Ruidoso for a day or two. She'll be on her R1100R and that bike runs like a sewing machine, never missing a beat. We'll probably end up in Santa Fe/Taos to ride the high loop up there thru Red River then back home thru Cimarron / Raton to the Texas panhandle (boring!).

Thanks for the good information though. One of these days I want to ride over to northern Arizona and Moab. I'll keep that road in mind.

 

[page5240]

The Enchanted Loop as the natives call it is one of the best rides in New Mexico. Taos to Questa, to Red River.....you'll feel right at home, most of the town is owned by Texans.....a stop at the Viet Nam Veterans Memorial in Angle Fire, actually just north of Angle Fire, then back to Taos......My wife and I have ridden it a hundred times or more....we lived in Albuquerque for 15 years.

Another great ride is US 64 from Raton to Chama....great high speed sweepers and no traffic.....

We have some great riding here in Arizona as well but you have to ride thru 125 miles of 100+ temps to get to it.......at least from Kingman, which is located in the Mohave desert. High temps in all directions...for at least a couple of hours.... A minor exception is old US 66 from Kingman to Seligman. I rode it yesterday and once I got up to about 5000 feet it was a pretty comfortable ride. Of course the 35mile an hour wind blowing across the road has to be ignored if you want to ride in the desert.

Long Distance Rider

 

[From MARS]

If you get near Truth Or Consequinces, the River Bend Motel has great mineral baths and clean rooms fairly cheap ~$70/night. Hwy 152 between TOC and Silver City is really fun, too.

Tom

 

[mymindsok]

If you get near Truth Or Consequinces, the River Bend Motel has great mineral baths and clean rooms fairly cheap ~$70/night. Hwy 152 between TOC and Silver City is really fun, too.

Tom

T or C!!

I spent the winter after 9-11 in T or C and while I liked the town, I'm really, really glad I didn't get stuck there! Is the theater still open? Last time I was there the sign said that movies would only be shown on Friday and Saturday nights, if more than 20 people showed up. Small town....! I used to soak at the River Bend back when it was a Hostel. Plenty of hot water and oh man, the girls!!! It also sits at a nice bend in the river and is a kool place to hang out, sip a beer and soak through the evening after a good ride.

Another neat place to stay there is the Sierra Grande Lodge. Not nearly as funky as the River Bend, it's a beautiful upscale lodge that has low prices (Compared to the real world.) and mineral baths. Plus, you can order up a massage!

If you have time to ride through any of the Gila National Forest.... Wow!!! Do it!

PS:

Jetted for 700 feet? IINM, that should be the same as sea level. OTOH, lots of NM is between 8K and 9K and your bike will definitely benefit from a jet swap before you get nearly that high

During my "big ride" last year I left the Cali coast jetted for sea level and hit well over 11K feet in the Rockies. At those altitudes, you would be wise to swap to a larger set of jets. In fact by the time I got to Tahoe (Much less the Rockies.) , I had jumped up a couple of sizes to keep the power up.

AFAIK, Bings are not "self adjusting". At high altitudes you have to open the jets up so the bike can get adequate oxygen in order to burn the fuel. A call to the Bing folks will get you an assortment of a few jets that'll work just fine and once you start using them, you'll learn a lot more about your bike.

 

[20774]

AFAIK, Bings are not "self adjusting". At high altitudes you have to open the jets up so the bike can get adequate oxygen in order to burn the fuel. A call to the Bing folks will get you an assortment of a few jets that'll work just fine and once you start using them, you'll learn a lot more about your bike.

Quoting from the Bing book:

"The Bing carurettor is less susceptible to changes in elevation than other carurettors in use, and in general does not require jetting changes for the idle and lower part-throttle settings. These settings can be compensated for by mixture screw adjustment."

It does go on to say that the upper part-throttle range will require lowering the jet needle to llean out the mixture. Plus continuous operation at higher elevation does require main jet changes, since this is where the control is for upper throttle operation.

So, while it doesn't do the total job of compensation, it does work fairly well in adjusting for altitude. I think what happens is that less vacuum is created by the air flowing through the venturi (less molecules of air), and thus the slide doesn't rise as high, thereby creating a slightly richer situation.

 

[page5240]

Let me get this right....there are people out there that tour the country changing jets as they change altitude.....I think not.....I've known hundreds of BMW riders in the past 40 years and have NEVER known one to change jets to ride in a certain part of the country.....long before fuel injection.....Bing users all.....

Long Distance Rider

 

[Bill Burke]

http://bmwmotorcycletech.info/bingcv-2.htm

Go to the end of this article for Fleischer's advice on higher altitude jetting.

 

[guenner]

Huh, I live at 6,800ft and this is the lowest starting point for my weekend tours. I am the first owner and I always use stock jet sizes and needle position. At 12,000ft and above the engine starts to idle very low and eventually stalls.

I never felt that I get more power at lower altitudes (i.e. Kansas). I know at higher altitudes I have to open the throttle a bit more ...and get that nice deep roaring sound from the carb intakes.

/Guenther

 

[jforgo]

Ditto. I live at 5200. the stock settings are fine. There is less air the higher you go, so that piece of the fuel/air thing is lacking. Your power will be a bit off, and fuel consumption up. Just adjust your fuel stops appropriately, and make sure your air filter is clean.

 

[lkchris]

Another ditto.

Ride more, wrench less.

Don't worry, be happy.

 

[dennisdarrow]

+3 or 4 on the thought of just getting out there and riding. Yes, you will use a bit more gas at higher altitude and perhaps a bit more throttle. For me, I have other things to consider when on a run than how smooth my idle is on top of Pike's Peak or other above 12k roads. Doesnt the grin take those worries away?

God bless and RIDE..........Dennis

Thread count DOES not equal credibility..............RIDE

 

[mcrenshaw]

Normally, I'm not one to worry too much about gas mileage. As long as the carbs aren't leaking on my boots and there is gas available every 100 miles or so (kidney's aren't quite what they used to be) we're quite happy to lope along.

Planning the trip is a lot of fun and my wife, being an IT director, is a whiz with Google Earth. We came across some really nice looking maps last night and when we saw the "No Scum Allowed Saloon" in White Oak, New Mexico, we looked at each other and said "we just gotta take that road!"

Something interesting always happens on the road and just so long as it's not a serious mechanical issue we can work through it. I keep the Anonymous book in the tank bag and it's come in handy a few times.

Having said all of that, I'm not going to worry about rejetting. We're not going over any of the really high passes like in Colorado. Hope to see some other beemers on the road soon.

 

[lkchris]

Yes, you will use a bit more gas at higher altitude ...

Probably not, actually.

Not as much aero drag in the thin air.

Plus, you'll be running downhill a lot.