one cylinder not firing

[jonko]

Hi all,

So cylinder #3 on my bike is not running properly. The header pipes for that cylinder just doesn't get up to temp. The bike is running just ok. It does feel like one of the cylinders might be off. I was able to do a compression test and it seems ok. Here are the readings (dry, cold):

#1 #2 #3 #4
120 128 135 118

I checked the spark plugs and have attached a picture. Plug #3 does seem very black, indicating a rich condition?? I also checked by grounding to the frame, and it sparks ok. I'm guessing it could be a carburetor issue, but don't know anything more. What should I be looking for? Clogged jets? Stuck float?

Pic one shows the headers. #3 is a completely different color from not getting to temperature. It also has a half or quarter inch dent in it. Possibly related?

Well, I would appreciate any help.

Thanks all!

 

[BlackNinjaZX10]

Check to see if that header screw is tightened. That should be the first thing to check. *Discolored pipes*

 

[r6_wheeler]

Have you checked to see if the coil is bad replace the coil with a known good coil. Next would be carb has the bike sat for a while?

 

[teg916]

That #3 plug looks wet. Is that oil on it? It could be a fouled plug so it isn't getting a strong spark. Usually if it is running too rich it will have black soot on it but it shouldn't be wet like that.

 

[elskipador]

3 looks wet to me. i'd inspect both the ignition system for #3 & the carb body/jets/float/etc... @ least you know the problem is limited to #3. i'd also get a fresh plug.

 

[sixtytwo]

Have you checked to see if the coil is bad replace the coil with a known good coil. Next would be carb has the bike sat for a while?

+1

This is on your '04 gsxr, right? My personal experience is that the direct ignition coils go bad frequently. A quick test would be to swap the #2 and #3 coils, and see if the problem shifts over to cylinder 2.

If it's on your older cbr though, then the ignition coils probably aren't the problem. It's my understanding that the older bikes had two coils for four of the cylinders, so if it was a problem with the coils, two cylinders would go out at the same time.

 

[elskipador]

its the f3

 

[jonko]

Thanks for the advice so far. I will check header bolts as soon as I have time.

I should have said so earlier. Its for my 98 cbr f3 with 54000 miles. It was recently recovered from theft. It was running like crap when I got it back. Rough idle, lots of sputtering and backfire. I figure it was water in the tank or gummed carbs. I used seafoam in the tank, and it seemed to clear things up a lot. Cylinder #3 was an issue before this, but probably not as bad.

Anyways, it's probably not coils since I only have two. I guess next is to check the carbs, but not really sure what to look for.

 

[Rob]

3 looks wet to me. i'd inspect both the ignition system for #3 & the carb body/jets/float/etc... @ least you know the problem is limited to #3. i'd also get a fresh plug.

This guy know his shite. Retest the spark thing with a new plug.

 

[Starshooter10]

that small of a dent while not GOOD, isnt going to cause a miss like your getting.

and from the info i know about F3's and what you have posted i'd rip your carbs apart

no 3 is wet but they all look too rich.

of could be wet from a number of things poor spark (replacing your plugs may help but you may also want to trim 1/4 inch off the plug wire and re screw in the boot. just to be sure.) to the carb dumping fuel. for that well it could be alot of things

 

[trhouse]

If you have an ohmmeter and measure the plugs from the center post to the side ground, any measurable resistance will mean it will not fire properly. It must be an open circuit. Any measurable resistance will short the spark.

 

[teg916]

If you have an ohmmeter and measure the plugs from the center post to the side ground, any measurable resistance will mean it will not fire properly. It must be an open circuit. Any measurable resistance will short the spark.

This is true, however if it passes this test your spark plug could still be bad. If the ceramic is cracked, your spark plug will spark internally (not at the electrode), and you will not be able to measure any continuity.

 

[hayabusafiend]

Easy test: Put the #3 spark plug in the #2 cylinder. If #2 doesn't fire, it's the spark plug. If #2 fires, then the #3 cylinder issue is something else.

 

[jonko]

So I just wanted to follow up on this thread. It seems that the problem has mysteriously disappeared. Whether it was a bad installation of the spark plugs, or seafoam continuing to do its work, I don't really know. All I know is that all four cylinders now gets up to temp...

Thanks everyone for their help!