Cylinder not firing

[Bscardina]

I have a 86 GL1200 Aspencade that was customized a cafe racer style bike. Faring, bags and trunk all removed. The bike runs but the #4 cylinder is not firing at idle. When riding at cruising speed you can tell that cylinder is still not firing but when you get on the throttle hard you can feel that cylinder kick in. Runs much better. I’m getting spark from the plug. Tested for compression and it’s good. I suspect a fuel issue. I took the carbs off twice and cleaned them. Don’t see anything there that I suspect would be a problem. Suggestions would be greatly appreciated. Thanks.

 

[D-50Dave]

On another thread recently, the suggestion was made to get an ultrasonic cleaner (under $100 at HF). I and many others have had good luck cleaning the uncleanable with them. Good luck, Dave

 

[kerryb]

Just about the time you're sure its the carbs, is when it's time to check the ignition system. My problem was a bad plug cap when I was busy working with mixture screws.

 

[dan filipi]

True, I had a shorted spark plug once. Iridium. Looked clean but no spark out of it. That was after messing with mixtures and probably a lot of idling. New plugs made a big improvement.

 

[Bscardina]

I’m quite sure that this is a carb issue. I’ve tested for spark at the affected cylinder and it’s getting spark. The spark plug is always dry when I pull it. Has to be a fuel problem. Besides the slow jet which has been cleaned twice, is there anything else that would prevent that cylinder from getting fuel at idle or slow speeds?

 

[pidjones]

I’m quite sure that this is a carb issue. I’ve tested for spark at the affected cylinder and it’s getting spark. The spark plug is always dry when I pull it. Has to be a fuel problem. Besides the slow jet which has been cleaned twice, is there anything else that would prevent that cylinder from getting fuel at idle or slow speeds?

All fuel passages are suspect, as well as air passages that help carry fuel in. Squirting brake cleaner through ALL passages is a common last test before reassembly. In addition, check that the fuel level is the same as other carbs and that the throttle butterfly and vacuum piston are unrestricted. also the fuel metering rod should be the same on all carbs (check the part number on it).

 

[kerryb]

Have you tested the plug caps for proper resistance. I recently learned that having spark may not be enough...it needs to be a good strong spark.
Your problem does sound fuel related, did you pass a cleaning wire through the idle jets?

 

[Bscardina]

Yes. I have a set of jet cleaning wires and ran them through the jets. I’ll try swapping the ignition wires on both ends and plugs between cylinders 2 & 4.

 

[85goldwing]

After cleaning the carbs in a ultra sonic cleaner, I use a water pic teeth cleaner to shoot water though all the jets to verify they are clean and flowing ok.

 

[85goldwing]

After cleaning the carbs in a ultra sonic cleaner, I use a water pic teeth cleaner to shoot water though all the jets to verify they are clean and flowing ok

 

[Bscardina]

What ultrasonic cleaner do you have? What is the cleaning solution capacity and what solution do you use? I may be in the market if I can’t find someone that has one.

 

[Workinman]

I have a Vevor 30 liter unit. If you want to do banks of carburetors without separating them you’re gonna need one that size. If I’m not mistaken, mine was around $250 or so.
The cleaning solution I got off of Amazon for about $45 I think. For 1 gallon. It’s just for cleaning carbs in an ultrasonic cleaner. I put that in along with 5 or 6 gallons of distilled water. A lot of people just use simple green or something of that nature but I’ve never tried that, so I can’t vouch for its effectiveness.

 

[Rednaxs60]

Yes. I have a set of jet cleaning wires and ran them through the jets. I’ll try swapping the ignition wires on both ends and plugs between cylinders 2 & 4.

You have a 1200. Right side coil is for cylinders 1 and 2, left side coil is for cylinders 3 and 4. Engine won't like swapping ignition wires between 2 and 4 cylinder.

I would check the coils for primary and secondary resistance. If resistance is good, can try swapping ignition wires, but think the issue will be elsewhere.

 

[ChickenWing]

You have a 1200. Right side coil is for cylinders 1 and 2, left side coil is for cylinders 3 and 4. Engine won't like swapping ignition wires between 2 and 4 cylinder.

I would check the coils for primary and secondary resistance. If resistance is good, can try swapping ignition wires, but think the issue will be elsewhere.

I agree with the issue that the left coil may need replacing, when at higher engine speeds the stator is pushing the high voltage but at idle the lower voltage is weak going to the coils especially the left coil.