HELP! New kid on the block (carb prob)

[earlybird]

I have gone cross-eyed looking for the right info here. There is soo much of it. Quite simply the problem with my recently aquired `79 xs1100 Special is it wont run at idle speed and does slighly back fire. I know it must be carbs but I aint got much idea. I need the process explained simply Also when out in rain ( we get a lot of it) it tends to go lumpy and lose power. Here`s hoping.

[Ivan]

Probably have plugged pilot fuel jets. They are in the bowl and under the cap in front of the main jet.

If it runs rough in the rain, a good test is to use a spray bottle (old windex bottle works) and mist water around the plug wires looking and listening for any signs of spark going where it shouldnt. That will usually get you pointed in the right direction.

Also check the tech tips section on pickup coil wires, they are a problem on these bikes, that could be causing the rough running.

[tarzan]

I second the idle circuits are restricted.Alos it could have a idle screw(pilot screw)broke off.If so it wont idle well and will run rough till you run it up a little.
A vacuum leak can also cause your symptoms.I would check all hose routing
and check for leaks at carb holders,vacuum nipples,and vacuum hoses.
Rick

[earlybird]

Thanks for that.
It runs great on a run and is very responsive, it goes down to 3 cylinders sometimes in the rain, it appears to be #2 plug which is effected, that is from the LH side of the bike. I asked them yesterday at the bike shop about the carbs and he recommended putting in some jet cleaner stuff in first (WURTH Injection Cleaner), which I have done. I think they didn`t want do it because they don`t like working on old bikes! Why sell them then me thinks!
I am sure we can get there.

[earlybird]

I think we are getting there. I have stopped the engine popping as it was doing slightly and had it idling for a while at just over 1000 rpm. I have ordered a carbtune set which should be with me by Sat at the latest. I have only had the bike about 1 month and the previous owner barely had it that long? Not sure why he let it go. At least it seems to idle better than before. We shall see. The number 1 exhaust pipe didn`t seem quite as hot to the touch as the others. So adjustment should sort that hopefully.

[03mach1]

Run some SEAFOAM thru it, I ran 2 cans thru mine before tearing the carbs down and didn't have much buildup of stuff.

[petejw]

You might also want to check you havent got any
broken tips on the mixture screws, youll have to remove and
inspect them to see if there broken.
Also wouldnt hurt to check out the pick up coil wires tomake sure none are broken.
Welcome to the forum.

[FJ111200]

Originally Posted by 03mach1

Run some SEAFOAM thru it, I ran 2 cans thru mine before tearing the carbs down and didn't have much buildup of stuff.

I don't think we can get SEAFOAM here in the UK.

That's also a good idea from petejw

West Wales eh. We were over there on Aberystwyth Promenade last Sunday.
Have you checked us out here at www.benefiscal.co.uk/forum . It's a bit hard to find when googling XS1100 owners in the UK.
Welcome to you by the way.

[MTaft]

Sometimes, if you take the carbs off before you take them into the shop and ask them to clean them, they will even if it is an older bike. I had the same problem with my local Yamerhamer dealer. I had cleaned the myself three times, but when they put them in there ultrasonic carb cleaner it did the trick. This might seem like a no brainer, but check to see if the exhaust pipes are loose where they connect to the engine. And there is an article on the forum about pick-up coil wires. My bike was running on two cylinders at startup, and by checking all connections and fixing a wire using the article I mentioned above, my bikie is now running fantastic. Good luck!

[CatatonicBug]

I would say it's time to take the carbs out and clean the jets. If the jets are clogged, the cleaner suff won't be able to get in the holes to do it's job. It's really not as hard as it sounds. It'll take a couple cans of spray carb cleaner, and a few basic tools. A couple hours of work, and you'll have them all cleaned up. The carbs are the biggest problem on these bikes, and if you don't clean them thoroughly, you'll notice it. Lots of things to get clogged in there, so it's a good idea to open them up and make sure everything is cleaned up. There is a tech tip on this site that walks you through the process.

[earlybird]

I have taken the carbs off-pretty straight forward. I noticed that the pipes were cross connected. On the pet cocks there are numbers for the pipes to correspond to the other gizmo (vacuum?) I noticed that below mixture screws #1 and #2 carb had sharp needle points fairly prominant sticking 1.5mm down where as #3 & #4 barely were visible. Should these needle points be part of the mixture screws. If so these are no longer in one peice. ? I wil take the carbs to a bike engineer to have his opinion.

[bikerphil]

Originally Posted by earlybird

I have taken the carbs off-pretty straight forward. I noticed that the pipes were cross connected. On the pet cocks there are numbers for the pipes to correspond to the other gizmo (vacuum?) I noticed that below mixture screws #1 and #2 carb had sharp needle points fairly prominant sticking 1.5mm down where as #3 & #4 barely were visible. Should these needle points be part of the mixture screws. If so these are no longer in one peice. ? I wil take the carbs to a bike engineer to have his opinion.

Gotta get those tips outta there, they should be ONE piece. Tech tip....

http://www.xs11.com/forum/showthread...=&threadid=138

[earlybird]

Instinct told me they were busted. No wonder the bike shop avoided balancing the carbs-they probably knew about it. At least I know why it was tempremental

[03mach1]

When I rebuilt mine, I had 2 broken tips on the screw adjustments and the other 2 were worn pretty bad. No wonder we couldn't adjust it properly.

[earlybird]

Well the good news is all the tip ends are out. They were trully stuck and took an engineer genius I know to fabricate a little gizmo to do the job. We took `em apart and diaphrams etc were really good condition. Clean out the float chambers and set the throttle stops. He couldn`t see how anyone could cause such abuse like we found.
Tip: To get mixture screws right. Screw VERY gently all the way in and back out 1.5 turns and that should do. ( He told me that ) Just waiting for new mixture screws and then hopefully she will be sounding sweet.