High Altitude problems?

[CUBuffs]

Hey all you high altitude XSer's. It's been a while since I posted but I have finally returned to Colorado after 16 years. My XS was running pretty well in the midwest but since I have moved to Castle Rock (about 6200 feet) I can't keep it running without the choke on and even then it runs rough. When I open the throttle it wants to die.

I have played with the pilot screws but with no success. Someone here suggested I might need to re-jet. Anybody have some thoghts on that? Thanks.

[xszgrider]

High Altitude Problems

I live in El Paso where the altitude is 4000 ft and my XS1100G runs fine with the stock jets. I have never taken this bike very far out of the city but I have ridden through your area several times and into the mountains with other bikes running CV carbs and never had a problem.

Only dirt bikes have I had to play with the carb at high altitude. Maybe, your problem is some where else.

Hope this helps,

[81xsproject]

Maybe I have this all wrong in my head, but seems to me the change to a higher altitude would result in running rich (less O2 to fuel ratio). It seems odd that it runs better with the choke on..?

[TopCatGr58]

Jesse,

You're right! Having to use the choke/enrichener just to keep it idling indicates very clogged/dirty pilot circuits!!!

Buffs, you probably need to pull the carbs and go thru them paying attention to the pilot circuit...cause IF turning the pilot screws in all the way didn't have any affect, that too points to problems with pilot circuit.

Don't know what if any mods you have on the bike, Indy filters, or aftermarket pipes? You "might" need to rejet LOWER than current IF you jetted up for any mods. But, if you're running stock, may not need to rejet, might be able to get by with slight float adjustments, pilot screw adjustment, etc.!
T.C.

[CUBuffs]

It appears I had it backwards. I was turning the screws out.

Also, I know from previously going through the carbs about 7 months ago (when I was still in the midwest) that it has stock jets on it but I don't remember the specifics. Additionally, the bike has 4 into 1 pipes.

I'll check the carbs out again but I know they were pretty clean before I moved. Thanks.

[Shuriken]

Where I ride my 79sf, the elevation ranges between 6660 and 5700ft.

I'll have to check my jetting. I have a 4-1 pipe, which helps. These bikes definitely notice when you ride them at these elevations.

But it sounds like you've got other fuel issues that you'd have to solve first. How are the plug colors?

Ben

[CUBuffs]

Gentlemen,

I pulled the carbs and found no blockages. I also set the pilot screws to 1.25 turns---they were turned out about 3 turns. After putting it back together it still ran rough although a little better. I then checked the plugs for fouling and found 1 & 3 were black/sooty, 2 was was black/wet, 4 was ok. I cleaned the plugs off and it idles much better and with the choke off. However when I open the throttle it is rough and sometimes will seem to get stuck. I sprayed the pipes with water and found that #2 was very hot with the other 3 running cooler and about the same. Any ideas here. Thanks.

[skids]

Assuming your float heights are right-on, before you go and mess with the idle screws again you need to make sure that the synch is good. OK, you might need to screw in the wet one a half turn just to keep it running and maybe the fluffy black one a 1/4 turn in.

[Shuriken]

I've experienced things in the past where I thought I needed to solve a carb problem and it turned out to be electrical, and vice-versa. There are so many things in the fuel and electrical systems that have to be working properly that they sometimes mask each other.

If you're quite sure your black box, spark plugs, coils, and pick ups are OK, then I'd focus on fuel. But if the bike is running fine one day and then craps out the next, I'd at least make sure your electrical is OK. I really had some strange plug color variations once when I was fighting a bad black box.

Anyway...

If my bike started exhibiting the same problems, I'd start thinking about stock configuration and would check everything agains that. However, as other XSives have mentioned possible plugged jets and so forth, do you have any reason to suspect that the carbs or jets or fuel system could have junk in it?

If my bike were doing what yours is now, this is what I would do, not necessarily in order:
1. Check and/or replace plugs
2. Check for good spark on all plugs
3. Check black box connections
4. How is compression? Does #2 have low compression?
5. I'd remove the carbs. Float bowls can be removed with carbs level and fuel level in float bowl can be observed. Does #2 look higher than the others?
6. Clean carbs. If you're ambitious, you can take the carbs apart and soak them, use compressed air, etc. If not so ambitious right now, you can just use a lot of carb spray cleaner and air. Are all the jets clean, especially pilot circuit? Is the gas tank rusty at all? Is their any sign of rust in the bottom of the float bowls?
7. Check diaphragms. Any small holes, rips, or tears? Check jet needle positions. Are they at stock configuration?
8. Check jet sizes. Stock? On my old 80g, I had to go down in jet sizes to lighten up plug color with stock bike at 6660 ft riding elevation. Also, I have a 4-1 on my 79sf and ride at high elevation. I did *not* go up on my jet sizes with the 4-1. The idea is to get away from black/sooty plugs.
9. Clean jets, passageways, etc.
10. Reassemble. Set floats to stock. Set jet needles to stock. Set pilot screws to stock (number of turns out). Do a pre-carb synch. Even if only by eyeball, make sure that when you open the throttle on the carbs that they all open and close the same. There is an article on bench synching the carbs...
11. Make sure your air cleaner box isn't loaded up with gasoline. Make sure air filter isn't clogged.
12. Does the bike start? Does it idle without the use of choke? If it does, will it rev? If it does both, can you ride the bike? If you can ride it, can you take it on a long stretch of road and kill the engine at wide open throttle and then check plug color? What are the plug colors now? If they are too dark, go down on the main jets. If too light, go up.
13. If the bike will idle, do a carb synch on it with a proper synch tool. This can make a huge difference in how your bike runs, but you have to have a proper idle, first.
14. If the bike does not idle without choke, perhaps your float levels are too lean or the pilot carb circuit still has a problem.

What is the elevation difference between where the bike ran well and CO, where it does not run well?

Ben