Can one coil output be bad?

[Coady]

When double checking my dyna s ignition with a timing light, on cylinder 4 the light flashes fine at idle but over about 1500 rpm it wont flash at all. On the other 3 cylinders it works fine at all rpm.

I checked both coils resistance; 5.5k and 5.4k across each and 22k ohms each plug cap to cap. I also pulled the ngk plug caps apart and cleaned inside and check the resistance of each one (all around 5k).

I also swapped caps and spark plugs for cylinder 4 too and it made no difference.

So I'm wandering if one side of a coil can go bad? Or if its more likely the lead? Or something else.

Thanks

[OldVet66]

Scrap the stock coils and get Dyna green coils and wires. Out of ignorance, I replaced mine with all new factory coils and caps and they had me chasing my tail for a year woundering why it never ran quite right. I don't think the Dyna S does very well without the matching coils. After I switched, it was like night and day at less than half the price.

[Coady]

Scrap the stock coils and get Dyna green coils and wires. Out of ignorance, I replaced mine with all new factory coils and caps and they had me chasing my tail for a year woundering why it never ran quite right. I don't think the Dyna S does very well without the matching coils. After I switched, it was like night and day at less than half the price.

I'm happy to get the dyna coils as it sounds like they will give a stronger spark either way, so Z1 ent. will be enjoying more of my custom.

I also recall that cylinder #4 had intermittent flashes of orange on the colortune when off idle too which would apparently indicate a low float height, but I checked the fuel level with clear hose and it was fine. And I've been getting the odd puff of black smoke too. In short I've been chasing what I thought was carb problems but now I suspect ignition.

[rustybronco]

When double checking my dyna s ignition with a timing light, on cylinder 4 the light flashes fine at idle but over about 1500 rpm it wont flash at all. On the other 3 cylinders it works fine at all rpm.

I checked both coils resistance; 5.5k and 5.4k across each and 22k ohms each plug cap to cap. I also pulled the ngk plug caps apart and cleaned inside and check the resistance of each one (all around 5k).

I also swapped caps and spark plugs for cylinder 4 too and it made no difference.

So I'm wandering if one side of a coil can go bad? Or if its more likely the lead? Or something else.

Thanks

It sounds like the plug wire may have a break in it, allowing the spark to find a quicker way to 'earth'. have you inspected them for cracks?

[chuck hahn]

Micro cracks also will produce premature grounding although the wire looks fine. An old coot taught me a trick that works 100% as long as the rubber isnt obviously torn or cracked to the core. Take the coils off and buy a can of 100% silicone spray at any auto parts. Heavily soak the entire wire with the spray and let ALMOST but not fully dry. Do this 3 or 4 times and this allows the rubber to absorb tons of silicone. At that point let them dry for a day and this will let the absorbed silicone "gel" so to speak. I had tons of problems with my 77 750 and even my 98 Shadow expecially when it was raining ior high humidity. I did as i was told and all problems immediately went away. In general though i have found that a coil either works or dont..never heard of one working but not emmitting the proper spark voltage.

[Coady]

Thanks for the replies.

So sounds like it most probably is the lead. Since they're over 30 years old I think I will try replacing them all though I am still tempted by dyna coils just for peace of mind.