Looks like my carbs have to come off again.

[XS1100 Newbie]

Looks as if i have to pull the carbs again. I have been fighting with adjusting them. They seem to synch allright, but i can't get them adjusted where i like the running. It cranks right on up there now, but at about 7000 RPM i need to let off the throttle just a hair to keep the speed increasing. For some reason it acts like its running out of fuel, but if i back off, it will keep climbing. I noticed that number three carb does not have as much response when adjusted. I wonder if one carb could be the problem. It is also very cold blooded after resetting the float levels, synching, and adjusting.

[CatatonicBug]

Did you colortune, or tune by ear?

What did you set your float height to?

[dbeardslee]

When you're syncing, the #3 carb doesn't actually change - it's static and you change the others to match its draw. On the 7k fuel starvation - have you checked to insure your gas cap vent isn't clogged? Crack the filler cap, and try it. If it doesn't exhibit the problem with the cap cracked, you probably need to clean the vent.

[XS1100 Newbie]

Float height at 24mm. Wet checked right at bowl slit level. This corrected the not wanting to rev over 5000, and made it run a whole lot stronger with the same 40 MPG. I understand that number three is a constant in the synching, but it does have it's own air/fuel mix adjustment. Tried the gas cap thing more than once with no change. Repaired pickup wires. adjusted valves, checked timing, and vac advance. Trimmed end of plug wires. It seems that maybe i just didn't get something clean enough in number three, or maybe the mixture screw is bad. The tuning was by ear.

[dbeardslee]

It is also very cold blooded after resetting the float levels, synching, and adjusting.

Could be an indication of a lean condition. Could also be restricted enricher circuits. If you've got them off, you might double check the little jets at the bottom of the float bowls to make sure they're clear. A bread tie with the paper stripped off works well. You do have the late model carbs, right? You can usually tell by looking at the diaphragm cover. If the ones on #1 and #4 are chromed and relatively thin metal, they're probably the late models. If the caps are all made out of the same material - aluminum about 3/16" thick - then they're probably the earlier ones. Over the decades you never know what's been switched around, so I just thought I would ask. Also, are you running and modes on the exhaust or intake?

[CatatonicBug]

You can usually tell by looking at the diaphragm cover. If the ones on #1 and #4 are chromed and relatively thin metal, they're probably the late models. If the caps are all made out of the same material - aluminum about 3/16" thick - then they're probably the earlier ones.

He's got a MNS, and IIRC, on the LG, the outer carbs are gold, and the inner ones are not. On the LH, all 4 are exactly the same, all gold.

[dbeardslee]

I have seen one '80 with the bastardized carbs that didn't have the plugs installed over the pilot jet tower. It would go to 5k and then it was like hitting a wall. If you have the late model carbs (as per Bug's description - thanks for the clarification) look down into the pilot jet tunnel. If you see a small orifice about 1/2" down, pointed at the main jet tunnel, then you've got the bastardized variety, and the towers need to be plugged. I don't know if the MNS's ever had these type installed, but being an '80 it's something to check. I'm just trying to figure out what we're looking at.

[XS1100 Newbie]

All four tops on mine are gold. I have not pulled them again yet, but probably will get around to it tonight. Modes??? I will pull all four down and look real good at the jets and all. I will try to figure out what it is you are talking about with the pilot holes.

[CatatonicBug]

All four tops on mine are gold. I have not pulled them again yet, but probably will get around to it tonight. Modes??? I will pull all four down and look real good at the jets and all. I will try to figure out what it is you are talking about with the pilot holes.

I doubt you will have the funny pilot jet tubes. On the MNS, the main and pilot jets are two completely separate tubes, fully accessible from directly below (or above, once turned upside down) with a screwdriver. There are no caps on the pilot jets like there are on the older model carbs.

[dbeardslee]

I doubt you will have the funny pilot jet tubes.

I do too, but it doesn't hurt to check if the carbs are off. Sorry - meant to say mods, not modes .

[XS1100 Newbie]

No mods on the bike at all. As far as i know everything except for the front forks, handlebars, are stock. 11500 miles.

[dbeardslee]

Have you run a compression check on it?

[XS1100 Newbie]

You know, i have not thought of the need for that. I guess it wouldn't hurt to know for sure.

[dbeardslee]

It will give you an indication of the condition of your valves, which could have a bearing on the low vacuum. Never hurts to know.

[XS1100 Newbie]

pulled the compression check. 100 lbs across the board. Could not find in the manual where it said what factory specs were though.
Dang, i just thought about what i done. I have to repeat the test. I did not open the throttle. The bike was warm, but not hot.