Altitude Compensation?

[JAGUAR]

BRINGING AN 81 XS1100 OUT TO COLORADO(7K+ FEET) FROM CONNECTICUT(SEA LEVEL). ANY TIMING OR JETTING MODS. REQ'D?

[Shuriken]

You'll definitely want to rejet. Your bike will choke at that elevation otherwise.

I'm at 5700-6700ft elevation.

You may end up needing to reduce fuel jet sizes by 3% per 1000 feet above sea level. Other XSives will chime in.

Ben

[Jerry]

Colorado is interesting...problem is you don't stay at any 1 elevation for long. I live at 5,400 - 5,500 feet, but within an hour ride is Independence Pass (12,095 feet) McClure Pass (8,755 feet) and Grand Mesa (average elevation = 10,000 ft). 2 hours away is Moab, Utah...elevation 4,025 feet.

Next bike I get is going to have fuel injection. My XJ runs rich most of the time with its OEM 112.5 jets.

[Shuriken]

This is the same problem I have - only with far less variation.

It's a matter of mileage: If I drive 90 miles one way I drop from 6700 to about 4500 or so. If I drive 45 miles another way there are 8000+ ft mountain passes.

Fuel injection on the XS has got to be sweet. The fuel injection mod needs to be sold as a kit specifically for XS bikes, with specifically created instructions.

What I mean by that is somebody sells acquires the throttle bodies, pressure regulators, computer, software, and combines that with custom XS instructions....

Ben

[tommystinson]

An interesting fuel injection tidbit: When Ferrari first fuel injected the 308 (I.E. 308 GTSi), it sucked so bad that owners tore off the fuel injection to put Webers on them. I'm wondering if the current Megasquirt/GSXR system people have used on the XS is a "set and forget" system, or needs a little tweaking now and then. If one of the enthusiastic early adopters of the Megasquirt system has gotten theirs dialed in well, perhaps they would make their program/settings available to others willing to take the plunge?

[sixtysix]

At the XS camp we had in Colorado, I only remember one XS running poorly due to Altitude. Jerry is right, you only stay at high altitude for a very limited time. I would say that if your bike is running rich right now you are in trouble but if it runs normally or lean I think you will be OK. And unless you are running WOT up the mountain adjusting the mixture screw will help some.

[pgg]

Jaguar, I doubt you'll get altitude hassles on an XS11. Even though they're ancient, you're still talking a pretty top-notch design here. Unlike cable linked carb slides, and along with the rare (for a bike) vaccuum advance system, the XS's choice CV carbs simply auto-adjust to the engines' demands. Sweet. And with the linked pilot-main design, a single main jet change up or down can cover your whole rev range. Even sweeter.

[Pat Kelly]

I have my 78 E set slightly rich (reduce header blueing and runs a little cooler on our 110 deg. days). I notice a decrease in power above 5,000 ft.
99.9% of my riding is near sea level