Cylinder 2 not firing and oil coated plug

[Justindrider]

I Just Bought My Xs this past weekend and cleaned carbs got it running but the number 2 cylinder isnt firing. it is getting gas, fuel out the exhaust and coated plug, and i am also getting spark when i groung the plug to the engine. i am good with engines but cannot figure out what is going on. I am starting to think that the timing of the spark is off. all the other cylinders run fine but that one any suggestions on what it might be?? thanks in advance

[cywelchjr]

Since the ignition system uses a wasted spark system if the spark timing is right for 3 then it's right for 2. So, you need to check for compression on 2 since you need compression, spark and fuel and it sounds like you have 2 of them on there, so I'd be concerned about compression on that one. Also make sure to put a good clean new plug in there, as once fouled a plug will often no longer fire on these engines, but I'd check the compression first, it may be that there is a bent valve OR that the valves are too tight on #2 so you have low or no compression.

[Justindrider]

thanks, but that was the first thing i did was check the compression before i bought the bike. and i just doubled checked it, all 4 are common compression at 140 psi. put new plugs in and no change. getting gas and spark to number two. so lost any other ideas? thanks a bunch

[cywelchjr]

There are only the 3 things involved. If you have compression, and you have fuel (which I'm not sure about) the only thing left is spark. The easy test is to swap the plug wires between 2 and 3 as those are off the same coil and fire together, if the dead cylinder switches then you just THOUGH you had good spark, and have what is most likely a bad spark plug boot or bad wire end (you can sometimes fix that by cutting off about 1/4" of the end of the wire after taking the plug boot off and then screwing the boot back on after making sure you have nice bright copper wire showing).

Your compression numbers are slightly low, but plenty high for the cylinder to fire, and being all the same it should be fine as it's in spec, just a bit on the low side of the spec is all. You've either got to be getting too little gas, too much gas or not a hot enough spark. Just to be getting spark and gas is by itself not enough if it's not within the right envelope it won't fire. But try swapping the plug wires first.

[Justindrider]

ok thank you thats one thing i havent tried yet. ill let you know how it goes. and yea the compression is a little but what do you expect from a 31 year old motor with 24,000 miles you know. but thanks again

[cywelchjr]

ok thank you thats one thing i havent tried yet. ill let you know how it goes. and yea the compression is a little but what do you expect from a 31 year old motor with 24,000 miles you know. but thanks again

24,000 is nothing. My original engine had at least 68,000 when I changed it, and that was for rod bearing damaged by gas diluted oil, the cylinders still had great compression and it still ran great with good compression and very little oil use. I'm not sure how many miles the engine I've got in there now has, but I've put about 15,000 on it since I put it in. It's not unusual for one to exceed 200,000 with normal care as long as it's maintained and not overly abused.

PS, it was still running good when I pulled it, just rattling pretty bad in the bottom end.

[DGXSER]

Original spec for compression is 142 +/- 10%, so all four at 140 is spec if you ask me. 120-110, now that is low.

First off, check your oil level, does it look high? My theory is that your float valve may be sticking open and flooding that cylinder which is why it will not fire and the plug is coated in gas and running out your exhaust. If that is the case, it is probably in the oil also! Change the oil before you go running the engine if that is the case.

[cywelchjr]

Good point on the compression, I've seen everybody reporting significantly higher, but that's pretty darn close to original spec. As for the other, your right, it was kind of in the back of my mind when I was thinking about the mixture needing to be spec. I think you'll agree though, given that the compression is right, either the spark is not really right, or the fuel isn't. There is either too much, too little gas or not enough spark.

[TopCatGr58]

Hey Justin,

I think Cy's on the right track with the spark plug wires/caps. As stated, it..the coil fires both plugs at the same time, out thru one....thru the engine..and then back up thru the other. The caps are resistor ~5k, but the contacts inside can corrode, which can prevent a good flow, so you get strong spark on 1 plug, but poor on the one with corroded connections and such. Take the cap off the wire, just unscrews, check for green corrosion, trim back some till you get to good copper. Also OhmMETER the cap, if way higher than 5kohms, then you can unscew the cap...remove the internal resistor, clean it's contact surfaces, check with ohmeter, if actual resistor is still too high, then get a new cap, otherwise put it back together with cleaned contacts, and it should then provide the proper current flow.

But yes, also check the carb. I had a stuck float that was flooding my #2 cylinder, and it wouldn't run right at all until I got it up into the mains.

So...yes, too much fuel will prevent that cylinder from firing.
T.C.

[Bulldog9]

Could be several things (as noted by others). Spark is probably the culprit, and if the coil is good is probably the cap, or a bad /fouled plug. You should be able to unscrew the plug end off the wire. If you have the length, snip off 1/8" off the end of the wire, clean the screw head on the plug cap and re screw onto wire. I would put some dielectric grease in each cap. You may also want to replace the plug caps period, as they can crack and dry out. This is a great way to weather proof and improve your weak ignition system.

It may also be an oil fouled plug from leaking valve oil seals. If I park my 79SF on the kickstand for more than a day or two the plug will foul. I pop it out clean it and it fires fine. These bikes don't have very strong coils, and fouling is pretty common and happens quite easily. Occasionally I will foul them if it stalls when cold and full choke, and off and on over the years I have had to pull the plugs. I use the hotter plug (been so long I forget if a 7 or 6 to help with this.

I have 130K on my bike and have never done more than minor adjustments, infact have never opened the carbs other than an occasional dropping of fuel bowls to clean out the spooge from the bottom and removal to clean road grime. Did a full brake rebuild a year or so ago, SS lines, new MC, rebuild wheel cyls. But I have owned this bike since 1984, and because I've only been riding it maybe 1000 miles a year my service is an annual oil change and fixing what is wrong. Never a tranny/engine/starter/final drive problem, always changed fluids, and serviced. YES I have the 2nd gear issue, but you learn to live with it. I have for 115K miles ;-)

She is due a new exhaust, and I am currently (finally) putting in progressives front and rear, and could use valve guide/oil seals, but other than that I'd ride in anywhere. These are amazing motorcycles and will last indefinitely if taken care of.