Author Topic: High Altitude Jetting--5000' (1,500m+) and above  (Read 14512 times)

Offline AZBiker

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High Altitude Jetting--5000' (1,500m+) and above
« on: November 11, 2011, 11:24:34 pm »
So what's everybody running?  I live at 5,000', but the good roads by my house go up to 7,000'.

My current jetting is 135/38.  Bike is currently equipped with Cali emissions gear but will soon be stripped to 49-state form.

Stock airbox with K&N and stock exhaust.

Bike has never returned more than 30mpg, even on the highway.  I forget what the CO & HC readings were but it barely passed even after having the carbs synchronized.

FM says I can go down to 122/35 because of the altitude. 

Prescott, AZ does not have a local dyno shop AFAIK and I'm not going to throw that kind of money at this bike anyway.  I just want to maximize my mileage.  HP is a non-issue, even the way it ran before it had enough power to get me in trouble. 

I don't lug the motor either, fwiw.
rubber side down,

Derek
93 Cali black & red

Offline Rick Hall

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #1 on: November 11, 2011, 11:43:15 pm »
So what's everybody running?  I live at 5,000', but the good roads by my house go up to 7,000'.

My current jetting is 135/38.  Bike is currently equipped with Cali emissions gear but will soon be stripped to 49-state form.

Stock airbox with K&N and stock exhaust. ...

Bought my '94 as a Cali model from a dealer in N. Phoenix. Been living in CO at 7400' for the last 13 years. Same basic setup as yours? Haven't touched the jets, run a K&N, stock emissions stuff, pilot screws dinked with many moons ago, ... I average around 38MPG, got 50+ MPG a few years ago, but I was escorting a Moped around the mountains at the time.

I wonder... has the fuel height in the bowls been checked? Got good spark? No air leaks?

Oh, are carbs are constant velocity, changes in altitude doesn't effect them that much. It's not *absolutely* necessary to change jets @ altitude, but a few do. I'm not one of them.

Rick
Rick Hall     1994 ZG 1000 "Sam"      xCOG #1914 (CO)
  GfNi H.P.   DOD #2040   1kQSPT 14.16   IBA #3274
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Offline AZBiker

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #2 on: November 12, 2011, 02:05:42 am »
Bought my '94 as a Cali model from a dealer in N. Phoenix. Been living in CO at 7400' for the last 13 years. Same basic setup as yours? Haven't touched the jets, run a K&N, stock emissions stuff, pilot screws dinked with many moons ago, ... I average around 38MPG, got 50+ MPG a few years ago, but I was escorting a Moped around the mountains at the time.

I wonder... has the fuel height in the bowls been checked? Got good spark? No air leaks?

Oh, are carbs are constant velocity, changes in altitude doesn't effect them that much. It's not *absolutely* necessary to change jets @ altitude, but a few do. I'm not one of them.

Rick

Airbox boots are new, as are the boot spring clamp things.  When I reassemble the carbs I'm going to check the static float height first and then the fuel level and make sure it's dead on.  I even bought the "most expensive plastic tube ever" from Kaw to make sure I get it right.   The spark plugs all look fine and the plug wires have been replaced with new ones from Murph's.

I'm sick and tired of pulling the carbs.  This is the last time I pull them.  If it's not right this time, I'll probably sell the bike and quit riding until I can afford something with FI.  I've already replaced both of the air cut valves (outer one was ripped) and the fuel-rail o-rings, they were rotten too. 
I never really "bonded" with this bike.  Nothing but V-motors on streetbikes for me from now on. 
rubber side down,

Derek
93 Cali black & red

Offline Outback_Jon

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #3 on: November 12, 2011, 06:59:56 am »
I'm sick and tired of pulling the carbs.  This is the last time I pull them.  If it's not right this time, I'll probably sell the bike and quit riding until I can afford something with FI.  I've already replaced both of the air cut valves (outer one was ripped) and the fuel-rail o-rings, they were rotten too.

Sounds like the carbs really need a complete overhaul.  Everything replaceable being replaced.
"Outback Jon" Gould *** South Cairo, NY *** COG #9506 *** 2006 C10 "Blueline" *** CDA #0157

Offline Motor Head

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #4 on: November 12, 2011, 07:28:37 am »
 Before making Jetting changes, the basics must be correct. Maintenance adjustments completed.  Ignition system checked, valve adjustment, and compression test, all would be a good Idea to insure engine is correct. Fuel Level in the carbs must be checked, and set if necessary. It would be best to make sure the Carbs have not restrictions, or damaged parts, such as blocked jets, air bleeds, transition circuits. Torn or leaking slide diaphragms, or Air-cut diaphragms. Vacuum leaks between Carbs and engine must be eliminated, also Air leaks between Carbs and Air-Box.
 So jetting for the A5 model is in the Supplement section of the FSM. You may have the Later model. But here this info is, and nowhere is a 138 main mentioned.

There are a couple of very cheap ways to make sure your Ignition is up to it. First Check both the Primary and Secondary resistance of both coils, and then the Boot that attaches to the plug, as it contains a resistor. If you have the Original plug wires, get new 7mm hypalon plug wire, available by the foot and 4' is plenty. You can replace it easily for a couple of bucks. Don't run a Spark plug that has an "R" in the part # as these are resistor plugs, you already have a resistor in your Boot that goes down on the plug. So D8ES, not DR8ES. This will give a Hotter Spark, simple stuff. Taking plug readings, after this work will show if it is rich.
« Last Edit: November 12, 2011, 08:41:06 am by Motor Head »
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Offline connie_rider

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #5 on: November 12, 2011, 01:48:41 pm »
Moved from another discussion.

Whatever a person does, they need to find jetting that is the best for both worlds.
Years ago I jetted for a ride in Colorado. Worked great but was awful when I returned home to Houston.  I clearly jetted too lean when I did mine.
Rejetting is a heck of a lot of work to do if you change altitudes a lot.

Soo,,,, my thought is (a person might be able to jett extra lean for Hi Altitude and add restricter in the airbox when you go down to the flatlands....)
My thinking is this might give you the best of both worlds..

Is this a viable solution?
 By the way, Steve join in with your thoughts.
    Have you already built a 2 min kit for altitude and do you recommend changing restriction if you use that kit at lower altuitudes?

In my case, I'm (Flatlander) going to install a 2 min Jett kit in my bike that Steve put together for use with his performance Cam.
If I get the chance to go up to higher altitudes again, my plan is to remove/reduce the restrictor.

Ride safe, Ted

Offline connie_rider

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #6 on: November 12, 2011, 01:50:00 pm »
Bought my '94 as a Cali model from a dealer in N. Phoenix. Been living in CO at 7400' for the last 13 years. Same basic setup as yours? Haven't touched the jets, run a K&N, stock emissions stuff, pilot screws dinked with many moons ago, ... I average around 38MPG, got 50+ MPG a few years ago, but I was escorting a Moped around the mountains at the time.

I wonder... has the fuel height in the bowls been checked? Got good spark? No air leaks?

Oh, are carbs are constant velocity, changes in altitude doesn't effect them that much. It's not *absolutely* necessary to change jets @ altitude, but a few do. I'm not one of them.

Rick

Rick, I always assumed that Sam was Jetted special for Colorado. I am suprised as you go like heck!!

Ride safe, Ted

Offline Steve in Sunny Fla

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #7 on: November 12, 2011, 03:20:14 pm »
135 and 38 isn't even stock cA jetting, stock CA jetting is 130 and 35.

I have my jets kits set up for altitude also, theres several of them running in your area, and I've gotten feedback of high 40's to 50 mpg from them. While your jetting is definitely an issue fuel level will also be an issue, especially if the bike has any age to it. Steve

Offline Outback_Jon

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #8 on: November 12, 2011, 03:59:20 pm »
Just out of curiosity, has anyone that changes altitudes a lot installed a Dial-a-Jet system on a Concours?
"Outback Jon" Gould *** South Cairo, NY *** COG #9506 *** 2006 C10 "Blueline" *** CDA #0157

Offline Steve in Sunny Fla

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #9 on: November 12, 2011, 04:18:39 pm »
dial a jet is junk. sorry, just the facts - Steve

Offline Outback_Jon

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #10 on: November 12, 2011, 05:38:09 pm »
dial a jet is junk. sorry, just the facts - Steve

Nothing to apologize for.  Like I said, it was just out of curiosity. 
"Outback Jon" Gould *** South Cairo, NY *** COG #9506 *** 2006 C10 "Blueline" *** CDA #0157

Offline AZBiker

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #11 on: November 12, 2011, 09:22:22 pm »
dial a jet is junk. sorry, just the facts - Steve

Good to know, I've seen them advertised for years.
rubber side down,

Derek
93 Cali black & red

Offline AZBiker

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #12 on: November 12, 2011, 09:32:28 pm »
135 and 38 isn't even stock cA jetting, stock CA jetting is 130 and 35.

I have my jets kits set up for altitude also, theres several of them running in your area, and I've gotten feedback of high 40's to 50 mpg from them. While your jetting is definitely an issue fuel level will also be an issue, especially if the bike has any age to it. Steve

I'm gonna be pulling the trigger on your 2 min mod jet kit next payday.  I don't have the patience to screw with this and reinvent the wheel.

BTW, the only replaceable parts of the carbs that aren't new are the jets, the floats, and the diaphragms.  I've already done the float needles, air cut valves, and fuel rail o-rings.  Removed my fuel screws and they look fine. 
I've even got the gauge to check my fuel level when I get them back together.  I'm going to check the static float height with a small mechanic's rule before I put the carbs together. 

I'm planning on using iso-heet as the liquid to check my fuel height.

I laugh now when I see a 4-cylinder on Craigslist that "just needs a little carb work."
rubber side down,

Derek
93 Cali black & red

Offline Steve in Sunny Fla

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #13 on: November 13, 2011, 07:29:27 am »
You'll like this kit, it works well. You may want to get with Jim Snyder and see if he wants to make an adjustable blockoff plate for you if riding at sea level is a concern. You can just use a larger foam block at lower altitude, but Jim's adjustable plate would be a cool, permanent solution. Steve

Offline Sparkie

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Re: High Altitude Jetting--5000' (1,500m+) and above
« Reply #14 on: November 13, 2011, 09:02:56 am »
OK just saw this. I have some experience with high altitude jetting in Flagstaff, Az. (7000'). I started with stock cali jetting which was a 130 main and 35 pilot. I changed to SISF orig jet kit which leaned out the main jet mostly. The main jet now is somewhere around a 120 or next size leaner, (Steve's trade secret). I didn't use the needle shim as I don't need that at my elevation, per SISF instructions also. With these changes and adjusting the fuel idle screw (close to 1 3/4 turns out) my bike runs like a whole new animal. It really smoothed out the low end throttle response and I consistently get 47-53 mpg. When I do ride at lower elevations down to sea level the bike still performs very well. There is a slight difference in that low end throttle response at sea level. Its not quite as smooth then as back home. The top end hauls a__ compared to stock. I'm also running SISF exhaust sprocket which is also an amazing boost to low end power. But I'm very happy with these jetting changes at both 7000' and when I go to lower alevations. I don't think his kit that I'm running was really even designed for higher elevations but its a huge impovement over the stock jetting. I would probably benefit from blocking my air intake at lower elevations but I haven't experimented with this. I did try blocking the intake at 7000' and did not like the effect. My personal feeling is I don't want to be restricting air flow at 7000', its already happening. Hope this helps, Mark