Help! cylinders not firing

[PorterTheCelt]

I am in the process of getting my xs11 up and running. Got the carbs cleaned and ready to sync. I went to warm up the engine to sync, and found that cylinders 1 and 3 aren't firing (corresponding headers are cool). Is there an obvious answer to this or am I doomed to back track my way thru the electrics to figure it out? The bike has a brand new battery and spark plugs, if that helps.

[TopCatGr58]

Hey Porter,

Okay, cylinders 1-3 have nothing in common. Electrical makes 1-4 or 2-3 for coils, both ignition coils as well as pickup coils. 1-2 and 3-4 are linked by the fuel system, same fuel line feeds each pair. You have 1 cylinder from each type of pairs that are not usually linked.

SO....brand new battery, and spark plugs. Troubleshooting begins....test for spark at each cylinder. The ignition coils are wasted spark design, they fire both wires at the same time, goes from one wire, thru the engine and back up the other wire. SO....both have to be grounded/connected to plug that is touching engine while testing for spark to work.

There is a rarer condition where you don't have enough voltage to the ignition coils, so they don't have enough energy to fire the primary plug...go thru the engine and then fire the second plug on the way back to the coil...so you can have the pairing like what you are seeing.

Folks will chime in asking if you have cleaned ALL of the harness connectors....they corrode easily and voltage is loss easily from corrosion/resistance. Are you running the OEM fuse block....another source of electrical gremlins. Also, plug wires to plug caps can corrode causing voltage loss....you can unscrew the caps, inspect, snip off 1/4" of wire at at time till you get to clean copper vs. green! Also built in resistor in cap can corrode causing loss! Can take apart, check with Ohmmeter should be 5-7kohms, if much more, clean resistor, recheck, if still high, replace plug cap!

Once ruled out electrical, then we have to ask how well did you clean your carbs, properly take them down to all removable parts, jets, emulsion tubes, etc.! The Pilot circuit is the most common problem, very small passage clog easily. Also, pilot adjusting screws on top front of carbs, you have the 78E, which has the very fine tipped pilot screws, the tips are easily broken off when performing the gently seated and then backed out 1.5 turns for beginning tuning step! When broken off, it clogs the pilot idle circuit, no fuel, cold pipes!

Check and report back what you did/done/ and what you've found!

T.C.

[motoman]

I am in the process of getting my xs11 up and running. Got the carbs cleaned and ready to sync. I went to warm up the engine to sync, and found that cylinders 1 and 3 aren't firing (corresponding headers are cool). Is there an obvious answer to this or am I doomed to back track my way thru the electrics to figure it out? The bike has a brand new battery and spark plugs, if that helps.

May try unscrewing plug wire cap and cut back a quarter inch of the plug wire and re-install the plug cap. If no change, remove the left side ignition cover off motor, and using both hands try stretching apart each wire. If it stretches, wire is broke internally and needs repaired. These ole' 11's are notorious for a broken ignition wire internally. The vacuum advance causes them to move back and forth causing an internally broken wire.

[PorterTheCelt]

Thanks for the quick responses! I'll check into all of these things.

For the record. I have not checked any of the above. I bought the bike less than a week ago. Bought the battery, plugs and fresh oil/filter. I was told that the carbs were gone thru last spring, and the elderly gentleman I bought it from lost interest, and just wanted a bike he could ride. The xs was his project for about 3 years. He had a fair amount of work done, because it is in pretty darn good condition for a bike this old. I pulled the bottom end of the carbs apart and cleaned what little there was to clean. They look like they were gone thru recently to me. None of the mixture screws are broken off. The float and main needles actuate freely. The floats are free. I had to trim back the gasket along the inner wall of the float bowls to free them (thanks to one of you gurus for that tip).

I haven't checked any of the electrics on the bike yet. I simply haven't had the time given life's demands, and the carb work I have gotten done. The bike also has the oem fuse block.

[PorterTheCelt]

http://i446.photobucket.com/albums/q...pstjrqdyqh.jpg

Im going to go out on a limb here, and say that this could have something to do with my firing issue. So I'm pretty sure I'm going to start here and upgrade to the blade fuses. That mess was tucked behind the bracket that the fuses are normally mounted to. I'll still go thru and check the other areas that have been suggested.

[BA80]

I'm going to say you've got carb issues. The 79 carbs have very fragile idle mixture screws and get stuck in the idle feed orifice easily.

If that's what it is the misfires will go away off idle.

Or, the pilot circuit is still dirty. A plugged pilot jet.

[ViperRon]

Run it a little on the 2 carbs then pull the plugs on the cylinders not firing if they are wet you have fuel getting to them normally gas getting threw will fire may not run right but will fire. So if plugs are wet the issue should be in electrical.

[BA80]

I'm going to say you've got carb issues. The 79 carbs have very fragile idle mixture screws and get stuck in the idle feed orifice easily.
If that's what it is the misfires will go away off idle.

Or, the pilot circuit is still dirty. A plugged pilot jet.

Meant to say get stuck and break off in the idle feed orifice.

[PorterTheCelt]

UPDATE: I went ahead and upgraded to blade fuses. That seems to have fixed half of the problem. I am now getting 1, 2, and 4 to fire. I warmed it up a bit, and eased it up from idle, and it seemed to run smoother yet. Header #3 seemed to get only slightly warm, and the bike sounded much better. I will likely be pulling the carbs again for another clean. Is there a tech thread on cleaning these carbs? I want to get it right this time.

The mixture tips are still intact. I made sure to check that the first time I pulled the carbs. I will pull the plugs this evening sometime, and see how they look. Progress made is always a good feeling

[Rasputin]

http://www.xs11.com/forum/showthread.php?t=36017
This will link you to the carb cleaning tech tip.

[MPittma100]

Engine Skip

Sometimes a float can hang up and stop fuel flow. This is most likely to happen right after a rebuild/cleaning. A new float bowl gasket is normally the culprit.

Tapping the affected carb float bowl can sometimes remedy the problem. Try that before removing carbs a second time.

When rebuilding with new bowl gaskets, always check for interference. Trim gasket as required.

You can verify if fuel is getting into the carb by loosening or removing the bowl drain plug.

[PorterTheCelt]

Update

I pulled the carbs and cleaned the pilot jets as best I could. I wasn't able to get the jets out. I actually ruined a screwdriver trying to break them loose. I'm going to guess that I didn't get them clean enough, because I am still having issues with cylinders 1 and 3 not running at idle. I checked the spark plugs and they have good spark, and are not wet. Thoughts?

[PorterTheCelt]

So I was able to get the pilot jets out, and it was definitely them. They were diiirty... She's back together and running now and just needs a minor tune to be ready for riding season. I took it for a short ride to nearby gas station, and loved every moment of it. Thanks to everyone who responded to this thread.