XS1100 Diagnostic Nightmare

[noeleo]

Kind of similar to NastyDude, I have a problem. First things first. My ride is a 1980 XS1100LG Midnight Special. This bike was parked for 4 years prior to my acquisition. Before that, it was only ridden 20 miles, and was parked for 19 years. It only had 65, yes sixty-five, miles when I purchased it August 12, 2004. OK, the problem. After cleaning the carburetors, resetting the floats, and cleaning the petcocks, resetting the synchronization on the bench, the engine fired up and ran just perfect. Throttle response and idle quality were amazing. As long as you are sitting still, the engine runs great. Now, engage first, ease out on the clutch, roll into it...CRAPPY. It feels like it is running on two cylinders. Sounds that way, too. Shift to second. Runs okay untill you get into it. Then CRAPPY again. STOP!!! If you really get into it in first, and the RPMs enter the 6000 range, it comes alive! Grab second, and GREAT! Back off and take third just to cruise, and CRAPPY again. Idle is good, and full throttle is good. Pull of the carbs again, clean, recheck, to no avail. If you just want to run say 50 MPH down the highway, it runs really poor if you are in the higher gears. Say you're turning 4000 in fifth gear, and just want to accelerate up a hill, maybe pick up a few MPH, when you roll the throttle, it runs again sounding like two cylinders. I've tried this without the air box, and rode down the road (deserted county road) and sprayed carburetor cleaner into the throttle bores one at a time and no difference was noted. Do you think I have an electrical problem, possibly pick up coils or vacuum/centrifugal advance? Your assistance would be appreciated. I used to own a 1981 XS1100SH, and know about how well they really run. I miss it. I just want to cruise, and IF challenged, give someone a run for his money, so to speak. I know this is not the fastest motorcycle on the roads today, but it is probably pretty far up the ladder. Thanks again for all your help.

[Ken Talbot]

Sounds to me like pick-up coil wires. Mind you, that's what I say any time somebody talks about intermittent running on two cylinders...

[chevy45412001]

welcome

First things first, welcome aboard. Now that that is out of the way you are one lucky #$@#*^^%$(*&&^%$^@#@&^%. Ok now thats off my chest,why would a bike with only 65 miles need to have the floats adjusted?That bike has not even been to operating temp. Nor has it even come close to the first break in oil change. Ok just pulling your chain...lol I'd go through the fuel and carbs yet again (not kidding here) then clean them throughly AGAIN (not kidding here either) Chances are good that the po put the bike up full of fuel and you probly got some real hard crap in the carbs and such. But i mean go through the WHOLE FUEL SYSTEM ,tank ,lines carbs etc. etc. It starts and moves so your one up already. Clean clean clean

[CRXSi90]

I don't know about me sometimes...I think I might be off my rocker...

That sounds like the upper vacuum slide boot things have holes in them. Once you get more air going through the engine (6000 rpm) while driving, enough vacuum builds to lift them. Also, it doesn't really take much to rev engines, so in my past experience with the boots (or I should say what I heard from a friend) you can rev all day and still have problems with the engine under load.

I'm sure you've been in that area if you cleaned the carbs, though, so I guess you would have noticed if there was a problem.

Just thought I'd throw this out there as "an issue".

Kevin

[fxrer]

I think Ken is onto the problem. My '80 SG exhibited the same problems you describe, ie running on two cylinders, engine dying, etc, AFTER I came out from the quarter car wash. It ran on 2 cyls, and died completely at first when engaged in gear. I was able to limp home for about 10 miles, until something dried out and presto, it ran fine after that. I suspect the problem was in the secondary igintion ie, coils-to-spark plugs. Since there are two coils, each powering 2 cylinders, I suspect one coil/circuit got wet and the bike only ran on two cylinders until it dried out.

It happened a second time, even though I was trying to be very careful to avoid spraying the plugs/coil. Now I hand wash it with a bucket and have seen no more problems.

Maybe you should clean and resistance check the igntion circuit, including the igniter. Good luck

[chevy45412001]

pick up wires

Sounds crazy that a person with an xs has to stop every 65 miles to fix the pickup wires.we should really be getting into how to convert to a Good system like just an XSample from an XJ.I think 90 might be on to something also with dry rot on the carb peases.

[DEmily]

I'd say if the thing sat for 20 plus years and was hardly used, it could be just about anything. Dry rote, corosion, pluged fuel system. If I had a chance at on with only 65 miles on it, I would go through it from tip to stern. I can see it now!!! It would be the perfect XS specimen !

[jetmechmarty]

My SG also behaves just as you describe right after I wash it. It doesn't seem to suffer when I ride in the rain.

[TopCatGr58]

Hey there Noeleo,

In 80-81, they started putting those brass caps over the Pilot Screws, which are the idle adjustment screws on the top of the carbs where they fit into the boots! Check yours, and if the little brass caps are there, then you really haven't cleaned the pilot circuit as thoroughly as you would think! The Pilot/idle circuit contributes considerably to the early rpm range and if they are clogged, it will run like a dog until you are getting into the transition to the mains, like you said, around 6k!

Aside from pulling the bowls off and cleaning out the insides, did you actually remove both the Main jet and center pipe=main jet screw, but it actually slides in,no twisting, and the pilot jet, it's down inside the tube next to the main jet? And then, you'll need to remove those brass caps, remove the pilot screws, and then spray thru the pilot jet hole to ensure flow thru to the pilot screw hole and out the most forward little pin hole in the carb throat.

Please read the carb tech tips regarding the pilot screw removal and settings.

Would also suggest checking your timing advance mechanisim for smooth movement, the grease may have gummed up after those decades of storage, clean and relube as needed so that it moves freely and returns to original position.

And as mentioned before, you'll want to BREAK it in before going full throttle, or you could destroy your rings/cylinders. There's an owner's manual in the links section to refresh your memory! Yes, I like the 81SH also!!

[noeleo]

Thanks to all who replied.

TopCatGr58, Your response was on the nose as far as what I looked for initially. The P.O. had already taken out the plugs and readjusted the carbs for a header that he tried for 20 miles. He said it ran really bad, do he put on the stock pipes. Anyway, yes, I did clean out the pilot passages, pilot jets, and removed the idle mixture screws (nomenclature?). The center pipe? Is this the brass tube that the throttle slide needle drops through? If so, I did not remove them. I wasn't sure how, and didn't want to destroy them. What's the easiest way to remove them?

Also, today I checked the vacuum advance with the side cover removed and the engine idling. It seems to move freely, but when the throttle is opened, it is kind of "bouncy". Is this normal? I didn't check it going down the road, and maybe I should.

Thanks again to those who shed insight on this problem. Please don't quit posting to this because I still haven't fixed it, and your information is invaluable.

noeleo

[TopCatGr58]

Okay, we're getting somewhere,

That big brass diffusor for the needle jet just slides out, but UP thru the top of the carb, you have to remove the top slide cover and slide, then remove the main jet, that screws into the other end of that large brass diffusor, then you can gently tap on it from the bottom and it will slide out the top, there is a slot cut into the side of it, so it needs to align when putting back together.

There are several little holes in the sides of this diffusor, and same goes for the smaller Pilot Jets, vs. the 1 large hole in the Main Jet! Ensure they are all clean as well!!

Make sure there are no pinholes in the rubber diaphragms to the sliders. Make sure they slide up and down without hanging. Then push them up, put your finger over the arced slotted hole on the top edge of the intake bell, and release the slider, it should stay up, or slide down very slowly. If it slides down quickly, you've got holes in your rubbers!!!

Your bouncy advance is probably due to where you have the vacuum hose attached. It goes on the little nipple on the actual carb BODY, not the larger hose/nipple that is on the rubber Intake Manifold.

Okay, have fun, come back for more if needed!
T.C.

[noeleo]

OK, guys. Here it is, almost a year later. GNEPIG and TopCatGr58 have replied to another thread that I started. Thanks to you. Can't believe the help you people have been. I will take off the carbs AGAIN, and replace the jets with the originals. Then we'll see. I've got just over 1600 miles on it, and absolutely LOVE this machine. When you roll up next to a 750 Ninja, and he shakes his head, not wanting to drag race, it really makes you feel good. Not that I street race, though. Anyway, even though I have some minor carb problems, it really is an enjoyable machine to straddle and coax down the highway. I really need to find a few pieces to complete the package. The PO took off the OEM handlebars, and threw them away. I could just PUKE. He installed drag bars, and they are really uncomfortable for me to reach. I have a broken back, and just can't seem to get comfortable. I need to find a original set of BLACK bars (it's a Midnight, remember?) to replace these. Can anyone help? I have a set of NOS 1980 Special handlebars p/n 3H3-26111-00 (chrome) that are available for trade material. Still in the package. I thought about powdercoating them, but I really would like OEMs. Thanks again for all the help. Now, I'm off to the shop to take off the carbs and finally get this thing lined out.

[superdave]

I'll give you one dollar for every mile it has on the odometer ! You shouldn't be bothered with it any longer than you have. I'm not kidding...

[Winterhawk]

That sounds like the upper vacuum slide boot things have holes in them

I was just thinking that it might be the boots not being seated properly. I've did that before and it acted similar.

Could be the pickups or wiring coming apart.

Had an XS1100 the other day that the secondary wire was intermitent. Saw it with the timing light.

[noeleo]

One thing I didn't think to mention was the fact that it starts and runs great when cold, even without the choke(enricher). Don't have to warm it up at all to get wonderful low rpm throttle response. Saw this mentioned in another thread and thought it might be useful. Went to bikebandit.com and found the pilot jets (42.5) and the main jets (110). Will replace them and try again when parts arrive. Meanwhile, I'll keep on riding...