No spark in 1/4 plugs

Putting my bike back together, just finished a carb rebuild, replaced coils and fusebox etc. I get all excited to start tuning my carbs, and the bike doesn't start. I check and I get spark at plugs 2/3. None at 1/4. I checked the coil, and saw the correct resistances on both sides so the coil is good. I checked the leads to the coil and am getting around 10 volts. I even swapped the lead and hooked the 1/4 lead to the 2/3 coil and the plugs fired. So the coil is getting power, just unable to transmit that to the spark plugs. Fuses are good, plugs are new, battery is good (with a charger on it as well to ensure voltage). I am stumped at this point, and decided to ask the forum for the first time. Thanks for your help!

Also, when the key is turned on the 1/4 coil gets 10 volts constantly, where the 2/3 coil sees none until the starter is pushed. Not sure of the significance of this quite yet.

 

Even new plugs can be faulty. Try one of the other plugs on #1 and see if it sparks when grounded to the head.

When you say that you swapped the lead, are you swapping the low voltage lead, or the plug wires?

If swapping the plug does not work, remove the plug caps from #1 and #4, cut the plug wires back about 1/4" and put the plug caps back on.

You may also want to try starting it in the dark and see if the sparks are jumping out of the wires.

 

Yes I swapped the low voltage leads ( orange and red/white wires). There are no sparks jumping in the dark, just swapped plugs and they work when grounded to the head. What would removing and cutting the plug caps do? I have continuity from cap to cap, and the ends were preassembled when I got them from Len so I'm hesitant to take them apart.

 

Ahh . the unmentioned details. We are so used to questions about the original parts that I assumed that was what you are woking with.

Just to be clear; when you swapped plugs you found that the #1/4 coil would make a plug from the #2/3 coil spark. Is that correct?

 

Sorry the plugs themselves worked. But the plug on cylinder 1 still didn't fire. So I decided to take the coils off. When unmounted my bike started! So now the trick is to figure out how the coil is no longer sending spark to the plugs when mounted. Im not sure how it could be losing spark, so Im slowly covering each contact between the coil and the frame in an old inner tube so that it is insulated.

 

The coils themselves are not grounded to the bike frame. Perhaps the connector that runs from the coils to the main harness has a loose terminal or wire in it?

 

Turns out that electricity was jumping from a bolt in the primary side of the coil to a bolt in the frame........just couldn't see it until I got lucky!