Bad Coil?

Heading to the Larz Anderson bike show this morning on my 72 Commando when it shut down like the key had been turned off. Checked fuel - fine. Checked spark on left cylinder - fine. Checked right cylinder - nothing. Rechecked left - nothing. Waited 5 minutes and gave it a kick - it fired once and nothing after. It did this several times and thinking it might be the coil I waited 15 minutes and it started and it ran fine for the 15 minute ride back to the house. It has a CNW 6 volt coil pack. I had another coil pack that I was going to put on my 74 so I used that one and headed back out to the show. My question is - does this sound like it was in fact a bad coil and if so, should I chuck it or is it likely to be OK.

Ubnfortunately my second try to get the bike show was not a whole lot better as I lost my clutch in almost the same spot where the bike died earlier in the morning. Turns out the lock ring that holds the clutch release body had backed off. Spent the remainder of the day fixing that problem and never did get to the show :cry: .

Welcome. Has the bike given ignition trouble in the past? Have you seen Dyno Dave's clutch info? http://atlanticgreen.com/ndnsclutch.htm
I journeyed to www.rice-o-rama.com today, hate it that it's the same day as Larz Anderson

No. The bike has run flawlessly. I have put about 1,000 miles on it this year. There was no warning when it happened - running fine and then shut down.

BTW - It has a Tri-Spark EI.

What ignition? Points? Tri-Spark? Boyer? Don't rule out broken wire.. until you wring it out with an ohmeter, they can act intermittent.
The clutch release ring.. have you been through the clutch/primary? Lot of miles?

I am running a belt primary and dry bronze clutch. Was working fine until the lock ring backed off. Got it back together and working fine now. I will check the EI wirning to see if maybe a broken wire but I have a feeling it was the coil since it would fire for a second if I let it sit for 5 minutes as if the coil had overheated. Once I waited about 15 to 20 minutes it started and ran with no problem. Maybe the coil overheated or overloaded (possible????).

JW 72Combat said:

I am running a belt primary and dry bronze clutch. Was working fine until the lock ring backed off. Got it back together and working fine now. I will check the EI wirning to see if maybe a broken wire but I have a feeling it was the coil since it would fire for a second if I let it sit for 5 minutes as if the coil had overheated. Once I waited about 15 to 20 minutes it started and ran with no problem. Maybe the coil overheated or overloaded (possible????).

Click to expand...

I don't run a belt drive, others here may have the answer for you. That retaining ring shouldn't come off unless there is a compelling reason.. how is the clutch basket bearing?

Sure, ignition coils can fail that way. I'd breathe easy once you put a few more miles on the spare, to make sure it wasn't an intermittent failure coincidence giving a false positive.

My small experience in life with bad coils had the same, fails when hot, spark comes back when you let it cool off reaction

capacitors / condensors may be wiewed with equal suspision . A coil over 10 years old , if LUCAS , ive found usually Kaput .

If your kill switch is still part of the ignition power feed, wire around it. Full power to the ignition goes through the normally closed points-type handlebar switch. It's not a self-cleaning switch. I made a short jumper wire and installed it in the big block of 10 connectors under the tank. What you describe is classic bad killswitch behavior.

You could probably clean it, but the above has been my solution.

My bike, with Tri-Spark, behaved exactly as you describe before I wired around the switch.

I found the same thing. Kill switch was killing my spark. I cleaned it real good and put conductive grease on the contacts. It's working great now. I'd be afraid to ride without a kill switch.
JD75

The kill switch has been removed from the bike.

I would still check power at feed to the Tri-Spark unit, both when all is cold and when all is hot, running and not.

Check the primary and secondary resistance of the coil, both cold and hot. I'd recommend also removing it from the bike and moving it around while you check those numbers. I've had coil test good in one position but bad in another. Newer epoxy-filled coils generally are more durable than the oil-filled ones. Check with CNW to find out what the resistance values should be.