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High Altitude Jetting

T

TxGSrider

Forum Mentor
Past Site Supporter
I'm taking a trip up to Estes Park Colorado (about 7500ft and going up as high as 11700ft) next month and am thinking of taking my GS along on a trailer to get some riding in (If my wife lets me-lol). It has "slingshot" carbs on it and has been jetted with my wideband for riding around here (about 600ft). I found a jetting chart on Jets R Us and it looks like I should drop 8-12 jet sizes.
Does that sound about right?
Also do you think I'll have to drop the needles, and if so,how much?
 
My gs1166 ED was WBO2 jetted at sea level, I rode the bike to Yosemite where there is a 10,600 ft pass. The bike loads up but it is still very rideable.

What i I would recommend is the ngk irridium plugs. They seem to burn off any fouling fairly quickly. I also had 3ohm accel coils which I?m sure did not hurt.

most of your riding is not going to be at 11k ft is it?

To to answer you question , I can?t see how 10 steps could possibly be correct . Maybe going from 140 down to 130 but watch out for predetionation when riding the 130 at home.

if you really want to do this take your WB and some main jets and see what happens from lowering by about 10. At least next Time you make the trip you are prepared.
 
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CV carbs mostly self compensate for elevation changes so I would expect the bike will stay rideable the whole way as posplayr says.


Mark
 
posplayr said:
My gs1166 ED was WBO2 jetted at sea level, I rode the bike to Yosemite where there is a 10,600 ft pass. The bike loads up but it is still very rideable.

What i I would recommend is the ngk irridium plugs. They seem to burn off any fouling fairly quickly. I also had 3ohm accel coils which I?m sure did not hurt.

most of your riding is not going to be at 11k ft is it?

To to answer you question , I can?t see how 10 steps could possibly be correct . Maybe going from 140 down to 130 but watch out for predetionation when riding the 130 at home.

if you really want to do this take your WB and some main jets and see what happens from lowering by about 10. At least next Time you make the trip you are prepared.
Click to expand...

http://www.jetsrus.com/FAQs/FAQ_rejet_elevation_and_temperature.htm I'd guess most of my riding would be closer to 8000ft and a little cooler and lot drier there. According to the chart it looks like going from 130s to 120s would get me close. Since were staying in a cabin I could bring some different mains and swap them out there if starts loading up.
 
TxGSrider said:
http://www.jetsrus.com/FAQs/FAQ_rejet_elevation_and_temperature.htm I'd guess most of my riding would be closer to 8000ft and a little cooler and lot drier there. According to the chart it looks like going from 130s to 120s would get me close. Since were staying in a cabin I could bring some different mains and swap them out there if starts loading up.
Click to expand...

I recall going over the pass at 10K ft and it is definitely a louder sound and alt is affecting the way the bike was running (BS36). I would go three steps on the Mikuni main and then move either up or down (one) depending on how the plugs looked. My motivation would be to make the least number of jetting changes (been there done that).

Most of the mountain roads around Reno are probably 4-5Kft.

One of the first rides on my bike was on a rally down to San Diego from SB. I stopped on the way to pick up some jets from RapidRay and was swapping out jets over the course of the stay. Too big of a main jet change could possibly start affecting your needle. You already have a lot of time invested in turning as it is. Keeping the changes smaller and simpler would be my approach.
 
I can't comment on the jetting, but Estes Park is gorgeous and some great riding around there.
You'll have a blast, just keep an eye out for moose in those blind switchbacks!
 
Sam 78 GS750 said:
I can't comment on the jetting, but Estes Park is gorgeous and some great riding around there.
You'll have a blast, just keep an eye out for moose in those blind switchbacks!
Click to expand...

I haven't seen any moose there yet, but the elk are like squirrels there. Lol!
I actually got permission from my wife to bring the bikes. I can't wait to get some riding in there!
 
I've ridden my bike all over Southern Colo mountains, the San Luis Valley is 7,000+ and did fine, going over Kenosha pass and Wolf Creek it did fine. I ride the mountains here in south central NM all the time, anywhere from 3,800 ft to 10,000ft +. I run 2 two stepsup from stock because of my K&N air filter and pipe and the bike does fine. Does tend to try and load up some at the higher elevations though clears out quick enough.
 
mrbill5491 said:
I've ridden my bike all over Southern Colo mountains, the San Luis Valley is 7,000+ and did fine, going over Kenosha pass and Wolf Creek it did fine. I ride the mountains here in south central NM all the time, anywhere from 3,800 ft to 10,000ft +. I run 2 two stepsup from stock because of my K&N air filter and pipe and the bike does fine. Does tend to try and load up some at the higher elevations though clears out quick enough.
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I appreciate that Mr Bill. It looks like youre starting about 4000ft @ Las Cruces so it was about 3000ft up to 6000ft difference in elevation for you. Im tuned to here @ about 650' and riding from 7500ft to 11500ft so about 6900ft -10,800ft difference in elevation so I'm thinking its going to need some tuning. But its good to know it may not need very much tuning to still run.
 
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Im heading out tomorrow and left the jetting stock but taking some smaller main jets with me incase I want to swap them out there. Since is got pods the rack can be puled and the mains swapped out in just a few minutes. Cant wait to get out there.
 
TxGSrider said:
Im heading out tomorrow and left the jetting stock but taking some smaller main jets with me incase I want to swap them out there. Since is got pods the rack can be puled and the mains swapped out in just a few minutes. Cant wait to get out there.
Click to expand...


Do Dyno accessory for your oversized vacuum chamber?


Have fun :).
 
I had a great time. I turned the idle mixture screws in 1/2 turn which was a little too much for 8500ft and not quite enough for 11000ft. Otherwise I left the jetting alone and it was a little rich but still very rideable. I had a couple great rides and am so glad I brought my bike out.
 
No main jet changes, just a minor pilot adjustment? :-k

Seems to support the guys that were saying "the CV-type carbs will do the compensation for you". :encouragement:

.
 
Steve said:
No main jet changes, just a minor pilot adjustment? :-k

Seems to support the guys that were saying "the CV-type carbs will do the compensation for you". :encouragement:

.
Click to expand...

They did "blubber" a little from being rich at lower rpms, but certainly rideable. I think it didn't hurt that the temps went from mid - upper 90s here a few hundred ft above sea level, to low 70's at 8500ft at the cabin, to "freaking cold" at 11500 ft (there are still patches of snow up there).

I was glad I got the chance to ride there... it is beautiful.
 
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