One cylinder not firing...tips

OK, I'm almost positive that I saw kind of a breakdown on how to ferret out what was the cause of a cylinder not firing, but try as I might, I can't find it today. So, here's my question. I went to ride my 82 XJ650 the other day and for some insane reason decided I should touch the header pipes (actually, after reading about it a lot on line, wondered if perhaps my bike wasn't firing on all cylinders). Low and behold, but cylinder number three just did not seem to be kicking out the kind of heat you'd expect. So, what is the recommended procedure for figuring out the issue? I seem to remember starting with something as simple as checking the plugs, but I'm not sure. I also seem to remember mention of the coils, but again, not sure.

Also, while I've got your attention, any suggestion on a set of coils? I know the Dyna 3ohm are the most popular, but they are a bit outta my budget right now, so, any other suggestions? Accel??

Thanks in advance.
Beardking

 

I would check the plugs first. One of the keys to trouble shooting is to check the simple things first. If that’s not the problem see if its getting spark if it is I would think that is a fuel problem but remember that even if it has spark when something’s under compression it takes more power to make that gap.

 

Sometimes it's something as simple as the tightness of the Plug Cap on the end of the Spark Plug wire. Insert the strands of some ignition wire into where the Plug Cap screws-on and cut them off even.

Add an inch of tight-fitting shrink-wrap to the plug wire's end and shrink it ... followed by a second application of shrink-wrap for strength.

Screw the Plug Cap back into the end for a "Sure Fire" solution to loose ends.

 

I had one heck of a time, I think after I did my valve shims. Was running on 1 cylinder, which means barely running.

Pulled plug, base up against head. No spark. Kept messing around. Tried to start again. Plug fell off head - nice hot spark when it was ungrounded by 1/4 inch.

Plugs didn't look bad - but clearly fouled. Probably all those trips back and forth to the barn this winter not really getting them cooked clean. Also, idle might be a bit rich.

Cleaned the insulators off and it purred like a kitten.

 

Are you talking about the end that connects to the plug or the end that connects to the coil? If it's the end that connects to the plug, that's a pretty secure connection currently.

I took my plugs out today and they were all a bit black and sooty, except the 3rd cylinder. It was black and a bit wet (like fuel). Just for the heck of it, I took the spare set of plugs that I have from before doing my carb work and put those in, as they were fairly clean. Took the bike for about 1/2 a mile ride and checked them and they are getting black and sooty again, except #3, it's black and a bit wet. To me, it seems like all are running a little rich and #3 is REALLY rich. Thoughts?

Oh, and I checked the spark (pulled plug, grounded it on the cylinder, hit start button) and it was getting fire.

I'm trying to get this thing completely ready for riding as I'd like to start riding it to work every once in a while.

 

Did the wet on that plug smell like gas?

I recomend hooking the clear tubing to check float bowl levels and see if the floats are set just right.

 

Hvnbnd, yep, smelled just like gas. As did my air filter (was checking to see if it was clogged, which it wasn't).

I'm going to have to do the float bowls tomorrow after I get off work.

 

Are your mixture screws accessible? Sounds like you might have an overly rich idle...look at this thread for more info...

http://xjbikes.com/Forums/viewtopic/t=2 ... crews.html

I'd go ahead and screw the #3 mixture screw down a couple turns, take the plug out and clean it off with an old toothbrush and then run it a bit and see what the plug looks like. I had the same problem on my bike.

If you happen to have a colortune, then colortune it. :wink:

 

Man, you'd think they would have made those freaking mixture screws more accessible. I just filled up the tank this evening, so it's going to be a pain in the butt to take it off and go at it with the colortune again. ;-) Oh well, you do whatcha gots ta do, right.

 

You can do it with the tank on...I can on my bike, anyways.

Use a 2" long hexagonal slot bit (the kind you'd put into a cordless drill or one of those quick-change bit holders), and you should be able to reach in there and turn it with not a lot of finger pressure.

 

air filter with gas smell and runs rich......I'd suspect float level.

Try the clear tubing to check float bowl level.

 

Well, I just checked the float levels (literally, my hands still smell like gas) and they are all within spec. So, tomorrow (hopefully) I'll pull out the colortune and see what I can find out with it.

One question, I know that the exhaust for the non-firing cylinder will warm up from the general heat around it, but I noticed that after letting the bike warm up for a good 5-10 minutes, it seemed to be up to about the same temp as the other 3. Is it a possibility that once it gets warmed up that 3rd cylinder kicks in? If so, any suggestions on that? I'm sure it's not supposed to do that.

 

I've seen this symptom before......plugged pilot jet. Not saying this is your problem, but if you've got the bowls off, it's easy enough to check.

 

The fouling of the #3 cylinder means something. That is where the vacuum line for the petcock attaches. I would check the petcock for leaking. This would produce a reich mixture for all cylinders but mostly for #3. Remove the fuel line and see if it leaks fuel with it set on "ON".
If you have already colortuned by the time you read this then I suspect you will have found it hard to eliminate the orange flame if I am correct.

 

Blue Maxim, actually, there is no line going from the #3 cylinder to the petcock. I have dumped the failure of a petcock that needed the vacuum line and I have installed a nice little cap over the vacuum port.

I did colortune tonight and no matter how much I turned the adjustment screw on #3, I didn't get any change in color. Any suggestions on this one?

Man, I really need a local person that knows about this and will work for beer or pizza. ;-)

 

Only thing I can think of is that you're turning the mixture screw the wrong way...turn it in to lean it out. If you've got it turned all the way in and that cylinder is still running rich, then it's possible you might have an obstruction of some kind somewhere in the number 3 exhaust pipe.

Ok, I can think of one more thing...your idle jet is way too big. Maybe a PO did a little modifying in there. :x

 

Well, I guess I'll have to look at the exhaust and see if there is anything there and if not, I'll be taking the carbs off Sunday when it's raining and check the idle jet because I turned the screw all the way in (carefully) and out and it didn't change color at all. The other 3 I could easily get yellow flame showing and backed it back down to a nice bunson blue.

 

So was the colortune orange?
If so it is rich on that hole?!

Why is another story...... Have you tried the tapping on the carbs?
I use about a 1/2" - 6" extension and tap on it with a ratchet (you have to be very careful not to break anything)

So what led up to this trouble again?
Did you go thru the carbs?
Remove any jets and change them or perhaps put a couple in the wrong place (say in the #3 carb?)
I'm grasping here...

 

Actually, no the color was a fairly decent blue on #3, just not adjustable. As for how it came about, for some wild reason I decided to check the exhaust pipes to see if the were around the same temp, and #3 was a lot cooler than the others. It ended up getting up to the same temp as the others, but the cooler part at first worried me.

I'm wondering if maybe I'm making a big deal out of nothing since after only a couple of minutes of warming up, #3 seems to get in line with the rest.

As for going through the carbs, the only thing I've done on that front was I pulled the float bowls off and cleaned them. I'm pretty new to the carb thing, so I was a little hesitant to break them down any further. I bench synced them and then put them back on the bike and colortuned them. Then it got cold and I didn't mess with it for around a month or so. Now I'm trying to get it prepared for the oncoming nice weather.

 

I just had another thought....(yeah, that happens occasionally :wink: ).

You might have something wrong with your actual mixture screw on the #3. It's got a tiny tip on it that could easily be busted off by a ham-handed PO. If the tiny (and I mean tiny) tip is gone, it won't be sealing the hole at the bottom like it's supposed to. I'd pull it out and have a gander, unless you've already had it apart and know for sure it's ok.

You might want to wait and see if any of the gurus chime in, as well. :wink:

I just read your latest post....maybe it's something you can live with if the flame is a proper shade of blue? If it's not fouling the plug, then I'd just leave it. I was assuming you had an orange flame in the #3.

 

No color?
Not firing ... No fuel???
Oily fouling of the Spark Plug?

Check that there's no obstruction in the metering at the bottom of the offending cylinders Fuel Bowl ... that would prevent the WELL from filling with fuel.

Likewise ... probe the slender, brass Siphon Tube for obstruction. This is looking like no fuel getting up-top.

Push some spray carb cleaner through All those ports.

 

If during the colortune you closed the mixture screw all the way in and didn't get a miss fire then it has to be getting fuel from somewhere. Without a vacuum petcock then the only other sources I know of is the float height or a leaking choke plunger or as fooglebinder said the screw is damaged.
When checking float height you need to let the fuel stand for a minute and see if it rises. This is the way to check for a leaking float valve. A high fuel height will allow fuel to drown the pilot jet and therefore bypass the mixture screw.
If the oring is damaged this would allow air to be sucked in from the top of the mixture screw and may not allow an orange flame. The higher you raise the screw the more air can get in. It will therefore be sucking air from a point past the fuel source, weakening the draft on the fuel so that no more fuel gets into the stream.

 

I don't know about anybody else ... but, I'm a bit confused; here?

The ColorTune -- IS -- Blue?
But, the 3 Cylinder misses, fouls a plug and the 3 exhaust is cooler than the others???

Swap the connections to the Coils and see if it will run better on the opposite set of coils. If it does ... dial-in 3 with the ColorTune while she's running good this way.

If you find that the problem shifts-over to #2 (or 4) ... You need to shake-down the ignition problem you're having.

 

I am too Rick. But I have been through this before and usually something creeps in that finally makes things make sense. One of those cases where I wish I could get my hands on the bike and so does the owner!

 

That's my sentiment too. If I could get my hands on that bike, then it might be alot easier.

Sorry, but when we help from afar all we can do is suggest blindly and go strictly by what you observe and communicate.


btw, my bike started to do something like what youre saying only on the #4 cylinder. cold pipe and all. I found the sparkplug cap had started to come apart from the wire, simple tighten and replaced plug and smooooth again.

 

Believe me, I wish you guys could get your hands on it too. I'm kinda running blind on this as well. ;-) H*ll, everytime I do something to it I run in to my computer to get an update from the gurus. ;-)

I'll try switching the wires tomorrow and see if it helps any. When you say swap the wires, you mean take 1/3 and put it on 2/4 and vice versa, correct?

Sparkplug cap: I'm assuming that by this you mean the cap at the end of the wire coming from the coil that hooks onto the plug itself, correct? I'm really not this much of a bonehead when it comes to mechanical stuff, I just don't know the terminology for some of it. ;-) And I know next to nothing about bikes. Good combo, huh?

 

You can swap the plug wires and caps between #2 and #3 (the middle two). If your problem moves to #2 then you know to look at the cap, wire, coil.

 

any update on the problem? Is it fixed? I am having the same issue, but I can see my coil is cracked.

 

So far, no updates. I've switched the wires as was suggested and it didn't help the situation. The last time I went out to check things out, I rechecked the floats and everything was just about perfect. The real pisser, I started up the bike and all 4 cylinders seemed to be working great. Took it around the block a couple of times and it ran ok, but it seemed to be surging a little. I'm hoping that I can get a local bike guy to take a look at it and give me his opinion on what I'm doing wrong.

 

If the situation is IMPROVING ... you're doing "something" ... RIGHT!

 

That's what I'm hoping. The only thing is, I can't figure out what I did to make all 4 cylinders fire. I've asked this a few times before, but never really gotten an answer, is it possible for a bike to only fire on 2 or 3 cylinders when you first start it up, but then once it warms up, all 4 kick in? If so, what would be the typical remedy for the initial non firing situation?

 

A clogged siphon tube or the metering ports in the bottom of the fuel bowl that allow fuel to rise in the fuel bowl well where the siphon tube extends down in to.

Loose set screw on enrichment valve activating fork allowing rod to rotate without lifting-up the enrichment valve body.

Bad spark plug, wire, cap, coil.
Bad coil ground.
Moisture inside cover causing difficulty with pick-up signal.
Pinched pick-up's wiring along the path to the ignitor.

Bad connection between harness and coils. Quick-connects corroded.

 

The good thing is, that you live in or near a large metro area.

There are no shops per say where I am, nearest big city is oveer 100 mi away.

 

If you switched the 2 & 3 plug wires then the problem is either fuel or spark plug.

I found (at least before my overwinter tune up) that periods of low RPM operation could foul a plug preventing firing. High RPMs and temps would clean it up. Oh, mine don't have to look very fouled to not fire either.

Surging is fuel/air. Thread is getting old so I don't remember:

Did you check valve clearances?

Sync?

 

where is that post or how-to on changing the wires in the stock coil housing? I remember it showing how you had to cut the casing then re-seal it up afterwards. I have a new coil on the way, but I wanted to hack apart the old one and see what's up inside there....possibly fix it for a spare.

thanks

 

Nothing to loose PghXJ, go for it. If nothing else, you could possibly repair the coil and press it back into service as an emergency back-up (this is provided it is the secondary lines that are shot, if the primary is burned out, it's done).

 

I have not checked the valve clearances. Admittedly, I'm a little nervous to break into that, but it might be my next step.

As far as the sync, I bench synced it when I took the carbs down and cleaned them, but I haven't been able to guage them yet as I am lacking the guages.

 

I believe the pimary is good, and one of the secondaries is shot.

so, does anyone know where that how-to is on cutting up the coil and reattaching new secondary wires?

 

Valves arn't too bad to check.

To sync buy 12 feet or so of clear tube the size that will fit over the vacuum attachments on the intake boots, attach the tube to a broomstick so it is a U shape, fill with 2 stroke oil to have 3 feet of oil in each side. Get bike warm, increase idle to 1300-1400 RPM and sync 2 carbs at a time (3 & 4, 1 & 2, 2 & 3) cost me NZ $4 for the tube.

 

Here you are:

Coil lead replacement

Hope that helps!

BTW the solid core lead is $1 a foot here

 

Thanks Kiwi....

I went down and cut up the coil and measured the primary. It was 2.7 ohms on both coils. The seccondaries were about 11.5k ohms on all but cylinder #3 which was 9.1k ohms. I re-soldered ignition wires on the #2 and popped a new wire on #3 and sealed it all up with JB weld. Just waiting for it all to dry so I can fire it up to see if the coil works again. I will be using the new one I ordered, but if this one works it will be a backup.



thanks for the help on finding that post.

 

Nice work on the Coil surgery. I started on one and gave-up.

You should be firing-on-all-cylinders ... and ready to rock for the Spring and Summer.

Now ... if we can just get a few of the new people to put their locations on the page below the Avatar ...

... and include their Bike Profile in the "Signature" feature ... maybe a few of them will get fixed-up and runnin' good for the season, too!

 

OK, so I've finally gotten started on taking down my carbs and getting them all cleaned up trying to get this issue taken care of. One thing that I'm wonder, are my jets correct? I'm attaching a diagram showing what I have found so far in my #1 carb. And for background info, this bike is all stock mechanically. The only non-stock items I can find are the turn signals I put on and the headlight.

 

Not sure about the jets, but that is a nice cross-section view of the carbs...I think I will save that for yet another reference if I ever have to dismantle my carbs.

Yeah, I hope the coil and wires fixes my problem...I really don't want to have to pull those carbs.

 

oh and Rick, I added my bike info in my sig.

 

UPDATE: Last night installed the fully cured coil, put new plugs in, re-adjusted the float bowls (2 was spot on, 1 and 4 were low and 3 was high) and turned the key...fired up immediately and hat hot hot hot exhaust on all 4 cylinders. Checked the floats and all 4 are just on the bottom side of the acceptable range, but they are even all across. Now all that is left to do is sync.....

I'll be riding soon

beardking...Hope you get your bike issue worked out soon.

Oh and for your info, all my main jets are 112.5 according to the text on them. I didn't read the pilot jets...I forgot. sorry.

 

Beardking those jets are all correct for the 650 Maxim. The Seca's have a 195 pilot air jet.
How did you measure the secondary resistance and come up with #3 being weak? Secondary is measured from one lead thru the coil to the other lead with the plug caps off. So you can't isolate one lead from another.

 

I was talking about the plug boots when I was saying #3 was weak...sorry if I confused you. That boot looked damaged, and the plug wires were old and brittle....the secondary of the coil was borderline when I measured it through the two plug wires with no boots. I determined that I needed new wires and boots, so that is what I did.

sorry for the confusion.

 

Confusion!? Why, that's my natural state!!@