Loss of one cylinder

[TrapperAH1G]

Riding on twisties and noticed bike wasn't running right, sluggish.  Pulled over and in checking it out, found that pulling the plug wire on the left front cylinder doesn't change how it runs.  Definite change in idle if I remove any of the other five wires.  From this, I assume the coil should be ok since the second plug wire has spark.  Changed plug, no joy.  Plug wire?  How hard is it to remove ends and replace just the wire?

Thanks for your thoughts, wisdom.

[Jims99]

Pull the plug, stick it back on the wire, lay it against metal and start the bike. You will be able to if it’s firing or not. The area can be changed but not sure how difficult that is. Butch Fowler and wood butcher make up coil packs with new wires even in different colors. May also be a clogged float (sticking) not getting fuel. You can’t try running a strong dose of B-12 or Techron to try clear it out.

[98valk]

Riding on twisties and noticed bike wasn't running right, sluggish.  Pulled over and in checking it out, found that pulling the plug wire on the left front cylinder doesn't change how it runs.  Definite change in idle if I remove any of the other five wires.  From this, I assume the coil should be ok since the second plug wire has spark.  Changed plug, no joy.  Plug wire?  How hard is it to remove ends and replace just the wire?

Thanks for your thoughts, wisdom.

the wire is attached to the coil with a plastic compression tube fitting like this but not brass
https://automation-renew.blogspot.com/2013/02/compression-tube-fittings.html

the wires are stranded cooper, and there is a metal spike inside the coil end that the cable is pushed onto.    
the plug end actually has a removable resistor. there have been some reported cases of one failing.  

from some research yrs ago the carburetor Honda engines all had the same coil/wire setup.

do an ohm check on the plug, it might be bad. 

A nice performance mod I did yrs ago and which I need to reinstall this yr is re-installing the hotter firing blackbird coils.

[h13man]

Well I have fouled two stock NGK's on my bike at two different times both times the plugs were just over 10,000 mi. on two different cylinders.
If you look in the OEM manual, 8,000 mi. change intervals. After the last time I installed NGK Iridium as they really perform great cold starting to the point I only use the "enrichner" at spring roll out only. I have 12,000 on them at this time. Basically getting all I can out of them as I keep a spare in the tool kit.

BTW, there a PDF floating around here somewhere showing how to rebuild the wires using stock components. I used the following:

https://www.speedwaymotors.com/Red-7mm-Solid-Core-Spark-Plug-Wire-20-Ft-,5117.html?sku=91064011&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQiAhs79BRD0ARIsAC6XpaVH24FToirTU7ukZyHMQuJiYQA7Vg0Z1KagAcFw2BPccdhc5HUqLBkaAkvkEALw_wcB

[John Schmidt]

You said no spark on #2(left front), do you have spark on #1...right front? Both fired by the same coil, the one near the front tucked under the tank on the left. I'd just raise the tank enough to get at the wires and check for bad/loose connections for the plug wires. Then check continuity on the #2 wire, you may have a bad resistor which is inside the rubber plug cover.

[TrapperAH1G]

Number 2 cylinder is the only one that seems not to change the idle when disconnected.  Changed the plug, no improvement.  Played around with the wire, connector and it cured it......for a while, then it lost power again.  Will check for spark tomorrow.

I run techron in my tank every 3rd tank or so.

[da prez]

  I just had one that was a coil break down. We gave the coil to a shop that knew how to test.
 I tried to find the OHMS test , but couldn't come up with the numbers.
  They said it would break down under load. Replaced the coil and all is good.

                                          da prez

[TrapperAH1G]

Finally got a day that wasn't windy and rainy.  Removed the tank, thinking I'd trim the wire at the coil, then change the plug wire if that didn't work.  As soon as I looked at the coil I saw that the ground wire nut was almost all the way backed off.  Tightened it down, put the tank on and connected the lines, fired up and all is good.  No idea why that nut was loose, the other ground wire nut on that coil was tight.

Thanks for all the input, suggestions.  Ride safe.  Tomorrow, Sunday, am riding with my son and grandson.

[Hook#3287]

Glad it was an easy and cheap fix

Can't remember hearing of this issue before.

[TrapperAH1G]

Well, Deja Vu.  Happened again, same cylinder.  No loose connections this time.  Getting spark to cylinder, has compression. Gas in carb bowl.  Plug not fouled, switched with another cylinder and it runs fine, while #2 is still "idle".  Have a couple of friends coming tomorrow to help.  Will keep you posted, feel free to contribute thoughts.

[TrapperAH1G]

Today, a friend and I worked on the bike.  Cutting to the chase, we determined it wasn't getting fuel at idle but was at higher rpm.  So, removed the intake manifold tubes on 2 and 4, removed bowl on #2 and then took out the jets.  Main jet was clear, idle jet (38S) was totally blocked.  Took almost half an hour using carb cleaner, very small wire and air to clear.  Put it all back together and it does better at idle but isn't totally cured. 

I'm running B12 thru it, letting it sit for a few hours, repeating.  Thinking with the jet closed I may have varnish/build up farther back.  Time will tell, but at least I can now tell a difference when I pull the plug wire at idle.

Oh, I now know someone in the past has changed the idle jets from 35S.  Mains are still 100's.

[Joe333x]

Today, a friend and I worked on the bike.  Cutting to the chase, we determined it wasn't getting fuel at idle but was at higher rpm.  So, removed the intake manifold tubes on 2 and 4, removed bowl on #2 and then took out the jets.  Main jet was clear, idle jet (38S) was totally blocked.  Took almost half an hour using carb cleaner, very small wire and air to clear.  Put it all back together and it does better at idle but isn't totally cured.  

I'm running B12 thru it, letting it sit for a few hours, repeating.  Thinking with the jet closed I may have varnish/build up farther back.  Time will tell, but at least I can now tell a difference when I pull the plug wire at idle.

Oh, I now know someone in the past has changed the idle jets from 35S.  Mains are still 100's.

B12 is good stuff, hopefully clears up the issue for you. Also having a colortune is a great tool to see the combustion in the chamber so you know if you have space and makes tuning a breeze. They seem to be out of stock but maybe you can order one if you call.
https://www.freedomracing.com/g4171-colortune-for-12mm-spark-plug.html?___store=default&srsltid=AfmBOopKZjEluVCg6aoNt6g396L-PXqjqAyHkBkQy_1ujJ2C0Rcqh3NZ-zs&gQT=2