Carb gremlin

[CaptonZap]

I have a 78 XS1100 that has developed a strange problem. I will be cruising down the highway at any speed greater than 50MPH, and one cylinder will cut out. I haven't wired thermocouples to see if it is the same one all the time.
To get it going again, I pull in the clutch, close the throttle, let the engine revs drop, and then get back on it. It is happy again, and does not repeat with any regularity.
Any ideas, anyone? CZ

[MindWebs]

sounds like the pick-up to me.

(Copied from a post by dbeardslee)
if you wiggle the pickup wires and the bike runs smooth, your pickups are probably fine. There's just not much there to go bad, other than the wires.

yes, the wire goes bad. it's a known problem.
see link to see repair method
http://www.xs11.com/forum/showthread.php?t=543

You do, however, have to have the pickup gap set correctly. If you look on the rotor you'll see a raised area on it, and a corresponding raised 'bump' on each of the pickups. You rotate the crank by hand until the raised area on the rotor is lined up with the raised area on the pickup. You set the gap by loosening one of the screws on the pickup and adjusting it's position for the correct gap. I usually just hold a fueler gauge in the gap, apply a little pressure to the pickup, and retighten the screw. Then I remove the fueler gauge and give it a final check. Then rotate the crank and repeat on the other pickup. They should be set between .5 and .7mm. I set mine towards the lower number just to make sure those old magnets are doing their thing.

[XSokieSPECIAL]

First of all, welcom to the site Capton,

From experience what you are describing sounds like a pickup coil wire going bad. Your probably losing 2 cylinders rather than 1 but at that speed it just feels like one.

Have you had it cut out under accelleration going through the gears occaisionally also?

The pickup coils is the first thing I would check. Plenty of good info here on that subject here;

http://www.xs11.com/forum/forumdisplay.php?f=35

One other thing, be sure your spark plug boots/caps are making good contact with the wire. They screw onto the wires and the steel core of the wire can corrode away causing bad contact. Trim them back about 1/4" and screw the caps back on if your in doubt.

[xs11lover]

Yup, I had one that acted the same way. When you started it it ran fine. After it warmed up and got opened up on the highway it would miss all over the place. After it cooled down it would run fine again. Get a tester and test the pickup coil wires, Make sure you pull on them a little when you test them.
Mine would show they were fine until I pulled them a little.

[BigRed]

Just a thought: you could bring a spray bottle with you on a ride, and next time it happens, let it run like crap for 30 seconds or a minute, then kill it, pull over, and spray water on the headers to see which pipe(s) aren't firing. That should help narrow down your search.

[Ivan]

Another common problem on these is the spark plug caps getting a bit of corrosion where they screw into the wire. Pull them and trim to clean wire, slather it up with dielectric grease and twist them back in. That situation will let the sark bypass the plug, or just not fire.

If its pickup coil wires it'll get progressively worse until it doesn't fire at all in that coil. Also check for the wires being held securely so they don't get rubbed on the timing plate.

Typically, I'd also say to check valve clearances with your description, but it seems the XS11 has a robust enough valve train that they don't have many wear problems, so put that low on the list. If it was a FIAT engine, you'd adjust the valves first, even if it was an electrical problem with the radio. Alas, I digress.

[crazy steve]

...If it was a FIAT engine, you'd adjust the valves first, even if it was an electrical problem with the radio. Alas, I digress.

Ivan, did you have a momentary lapse of reason and actually own a Fiat (aka Fix It Again Tony)?

'78E original owner

[Ivan]

Ivan, did you have a momentary lapse of reason and actually own a Fiat (aka Fix It Again Tony)?

'78E original owner

Hell yes I owned one! It was a 78 X-1/9. It was a badass little car, except for the engine. If I could find one now, I'd transplant a drivetrain out of a Focus or Cobalt and drive the wheels off that thing. It had the lines of a Ferrari, The targa top of a Porsche, the handling of an F1 car and the reliability of an alcoholic meth head on a road crew. I got more trim because of that car than any other.

[FANNING507]

Really glad I caught this thread!

I have the same problem only at 45mph or higher and only when it is warmed up thoroughly. Went thru the carbs again and again, thinking I have a spot blockage. Will check the pickups tonite. I haven't had this much fun since the fuse box kept giving me different readings, and I thought it was a malfunctioning multimeter. As it warmed up the conductivity of the fuse holders kept dropping. Different readings each time I checked it. But it ran great at 70 degrees or below. Swapped it for TC's and no problems since at that location. Kim

[81xsproject]

With the age of these bikes, I recommend to ANYONE that hasn't fixed their pickups to do it. Problems or not. Sooner or later it will get you. Most likely sooner.

[CaptonZap]

Carb Gremlin

Well thanks guys,
Since the consensus is the pickups, they will get checked. I won't be able to test the repair, since the bike is down for completion of deferred maintanance.
Crazy Steve, I noticed that you have a 78E. I have a 78 that I bought from the original owner, and I don't know if it is an E or not. It has the air over on the front forks, and the bottom axel cap on the left fork leg, which, according to the Clymers manual I have, was indicative of an SF model. Is there something in the serial number that would identify the model? The number is 3H5 004506.
Thanks again, everyone. I'll be back with more questions as I go through this bike. CZ

[CaptonZap]

Carb gremlin

What a site!
I just went to the search function, typed in "model number", and Bingo!
Seems it is an '80 1100F model. Guess I'll have to find the title and see what it says.
CZ

[DGXSER]

FYI - the official letter designations correspond to the year. As in

78 = E
79 = F
80 = G
81 = H

The you get the supporting letters for Specials and Midnight Specials of S and L.

So a 79 Special is an SF, an 80 Special is an SG and 81 Special is an SH, and an 80 Midnight special is an LG and an 81 MNS is an LH.

But production year did not follow calendar year.