Cylinder #2 Not Firing

[pgilliam1]

The third cylinder from the right (looks on the diagram to be #4 - looks like the cylinders count straight 1-6 left to right) isn't firing at all. I didn't realize this until I felt the exhaust headers and that one was cold when the others were hot. New spark plugs about 200 miles ago. I just got this bike and have had idling issues but I thought it ran OK as it never seemed to miss a beat.
My question for you experienced wrenches on this bike, is what would be your best guess as to the problem? Do these coils have issues or anything that commonly occurs on these bikes to cause this? That would help in my troubleshooting. TIA.

[pgilliam1]

Too late, I'm afraid I've really screwed something up. I started the engine with the spark plug out. I Attached the spark plug to the wire and was going to ground it to the block and see if I had spark. The noise when I started the engine was awful so I shut it off. I reinstalled the spark plug and now I have the worst/loudest tapping sound coming from near that cylinder. What have I done?

[Rick Pope]

I would guess that there might have been a piece of gravel, or possibly a fallen nut or washer, down in the well along side the plug you removed. Do you know someone with a bore scope?

[pgilliam1]

I would guess that there might have been a piece of gravel, or possibly a fallen nut or washer, down in the well along side the plug you removed. Do you know someone with a bore scope?

I will ask around for the bore scope. So, you're suggesting that running the engine with the plug out should NOT have caused a problem, other than a possible contaminant falling into the cylinder? That's what I thought, but the noise is bad. What are the chances of getting something out of there without tearing the engine apart? I'd think pretty slim.

[daves79x]

The first thing you do is blow out the head with compressed air before removing any plugs. That area is a magnet for debris, as Rick said, both falling and road. Something had to be in the plug well and fell into the cylinder when you took out the plug. Being #4, you wouldn't have seen it. If it's metallic, a small extendable magnet will get it out, if it didn't imbed itself in the piston. If it's gravel, it'll be a bit tougher. In any case, you very likely bent a valve or 2 unless it was really small. I'm just rebuilding an '80 engine that had a screw drop into #6. Kind of made a mess of the piston - someone previous to me had the head already fixed so I don't know what damage was done to it, if any.

Why did you feel the need to start the engine with the plug out to check spark? Just turning it over with the starter and plug grounded will give you a spark reading. Probably didn't matter in this case since almost surely something fell into the cylinder and you didn't realize it anyway.

Your firing problem WAS just carbs, I think, but now you have a bit more to deal with. The coils fire cylinders in pairs, so very likely you'd have a problem with #3 also if it was that.

Dave

[pgilliam1]

Thanks Dave. I did blow the plug area out before I initially replaced the plugs, but that's been over 200 miles ago and I have done a lot of work to it since, so maybe something fell into there. It sounds like a bent valve. That's just the way I've tested plugs in the past. If not the coil or wire or plug, what else could the lack of spark be?
About now, I feel like a complete dolt.

[daves79x]

You never said whether you had spark to #4 or not - so you didn't, or didn't get to actually check it? I suspect you do have spark there using a new plug. Again, it is likely a carb problem, but I'd check all coil connections and grounds. Remove each plug cap, inspect for corrosion, and trim if necessary, then screw them back on tight.

Yes, to someone not familiar with a CBX, they do seem to run pretty well on 5 cylinders.

You can adapt a small tube on the end of a shop vac hose to try to suck out any non-metallic debris from the cylinder. You will have to remove the tank and get the area as accessible as possible. #s 3 and 4 are tough with the engine in place. I'd remove the front engine hangers as well.

Let us know how you make out with the investigation. Removing the head isn't the end of the world and can be done with the engine just tilted, but a lift is nice. Be prepared for shock at the cost of a head gasket.

Dave

[cross]

Yes, you most likely have something that fell inside. You should be able to buy boroskope at auto part store or harbor tools and you can always return it.
I would take Dave's suggestion and use shop vac but still you should use boroskope first to make see what's in there and after vacuuming so you know if you got it out.
Goodluck

[pgilliam1]

Sorry for the lack of replying, but I went to Florida for a short trip - back today.

I will get a bore scope by some means and inspect and let you know. I will also try the tube and vacuum to remove debris from the cylinder.
The sound is a very loud tapping with the engine running. Sounds like a valve way out of adjustment. I don't want to run it again until I inspect things as much as possible and as soon as I do I will post my findings.
When I removed the spark plug it was wet with gas so I'm assuming there's no spark. I never was able to check for spark because when the engine started, the noise was so bad I cut it off.
This whole episode really put a damper on my Florida trip. I'm still beating myself up for what I've done. I was really looking forward to riding this bike and that feeling was growing with every ride.
With time, this too shall pass.

[cross]

What I found on my bike before I took plugs out, was piece of broken cooling fin that was sitting next to the plug, along with some sand which I blew out with air.

[daves79x]

Lots of these bike have broken central cooling fins due to someone putting a plug socket over the fin instead of the plug, and twisting. Those are usually too big to fall into the cylinder.

Seriously, let us know what you find.

Dave

[pgilliam1]

No broken fins or debris found with inspection mirror around the plugs, and the other plug holes were clean as well.
I attached the largest tube that would fit into spark plug hole to a fairly strong vacuum. The vacuum brought out very fine black sand like bits and some were damp with what smelled like weak gas. I tried cutting the end of the tube at an angle and twisting it, but still nothing. Some of the particles that came out were magnetic, so I stuck an extendable magnet into the cylinder, but no luck there either. The piston is low in the cylinder so I may try turning the engine at the crank bolt and raising it a bit and trying the vacuum again. Guess I'm going to have to get a bore scope.
Is there any chance that leaving that spark plug out and starting the engine could have done anything else? TIA!

[cross]

I don't think so but there are people here who know more

[pgilliam1]

I changed the subject of this post so I wouldn't confuse anyone - It is #4 cylinder that is in question.
So, when I turn the crank from the bolt, there is a definite STOP when cylinder #4 is near (or at) TDC. I can get passed it by gently applying a bit more torque, but I can easily feel it there.
My hope is sinking -

[cross]

I would not turn the engine at all anymore as you can damage it more.
Get the inspection camera to see what is inside and prepare to take the head off.
It should not be that difficult