Bad Coil?

[waynek]

My specs...1979 GS1000L 31K
The Problem- When I take off the plug wires to either #2 or #3 (wires coming from the same coil) the engine runs with no change...so it's only running on 2 cyls...there's no spark from coming from 2 or 3???
Does this sound like a bad coil? they look like the stock coils
thanks in advance

[nert]

Could be bad coil. OR, could be you have no B+ ignition power to feed the suspect coil. OR, could be a problem with the points circuit for that coil. Like shorted wire, point set that don't open, point set that doesn't close bad condensor. OR, could be a problem with the spark plug wires themselves, or even (2) shorted spark plugs.

[DickV]

Bad Coil?

I recommend that you remove the questionable coil and take it to your local motorcycle/automotive service dept. and ask them to check it using a coil tester. I am convinced resistance readings are not sufficient measurements to determine if a coil will work under load. I found a local motorcycle dealer that tested two coils for me at no charge, both coils were bad although resistance readings were not too far from spec. The parts dept ordered OEM coils (for my 1982 GS450TXZ) and I had them within 3 days.

[Billy Ricks]

If you're still running a points ignition you could have a bad condenser or point gap has slipped.

[waynek]

I had the bad suspect coil tested and it's dead. now I'm wondering how long I've been running with 2 cyls....

[chef1366]

Switch the coils and see if the problem follows.

[Rocketman]

On my '82 GS850L I replaced both coils with high output Accell coils, new wires, caps & plugs, as well as changing out the old ignition with a new Dyna S as ignition pickup signalling the coils was suspect. I don't know if you're bike has electronic ignition like mine, but that swap gets me plenty of good, strong spark now.

[Billy Ricks]

Switch the coils and see if the problem follows.

Good advice here. Switch the supply wires to the coils and if the plug wires will, reach you need to switch the inner two to the outside cylinders and the outer two to the inside. This will let you know if it is the coil or further back in the ignition.

[1979GS550stl]

Experiencing no spark in just ONE cylinder

I just successfully put fixed leaky carbs on my 79 GS550 (thanks to help and advice from several of your posts, it started up rebuilt on the first crank), and now I'm having a new problem - no spark in one cylinder. First I'll try swapping wires, but what's the next diagnostic step after testing the wire when only one cylinder isn't firing? Ground? Points?

I too wonder how long I've been riding around on three. The bike had a surprising amount of power and ran very smoothly.

Does riding around on less than four cylinders do any damage to the engine? My last few long rides last season it felt a little sluggish. But I'm easy on my old girl, so I guess I didn't really notice the power loss. I may have put a few hundred miles on it, blowing off the occasional pop or miss, riding on three cylinders.

Thanks for listening. -Bryan

[chef1366]

Check your spark plug wire lead. Screw off the plug cap and cut a little off the end of the wire till you see nice shiny copper and screw it back on.

[1979GS550stl]

Good idea. I forgot the caps screwed off like that. Thanks.