What happened to my coil ?

[twincamzz]

'61 Pan with 12 volt system. Running Accell super coil ( 3 ohms ). Wiring checks out for continuity, have 12 volts running to coil from ignition switch, good wiring from coil to distributor. Bike had been running fine, although it is still a project in the works & has not been ridden regularly. Battery has 12.7 volts with motor off.

Last night while checking something out, I accidently left the ignition switch on for about a half hour. Finally noticed that switch was on & coil was HOT. VERY HOT. Let things cool down & checked the coil out this morning by removing a spark plug from head, reinserted it into plug wire & grounded plug to motor. Turned ignition on & opened points, no fire at plug so I assume coil is fried.

Is there another way to check coil to see if it is really fried ? Read on another forum that if I test with ohmeter across the 2 small terminals & do not have continuity then coil is toast. Right now there is no continuity there so I assume coil is a goner. Correct assumption ?

Since ignition was on for extended period of time without opening points to release energy in coil, could this be what fried my coil, or is this indicative of another problem somewhere ?

[Pynzo]

Sounds like you cooked the coil, or the condenser. Did the Points fuse together? Try grounding out the coil someplace other than the points and see if it fires.

[twincamzz]

Points are not stuck together, however I do see a small spot on face of points. I've got a spare  condenser laying on shelf, I'll swap that out & see if that makes a difference.

Not quite sure I understand what you are saying about testing coil. Do I simply take wire from coil to points loose at points & ground it out at the motor case  & see if plug fires when wire is grounded & ignition is on ?  If that's the case then my coil is toast because I just went to garage & tried it & still no spark.

Thanks for the advice ! Been a looooong time since I messed with Points, etc.

[rigidthumper]

It should fire when the ground is removed, not when the ground is applied. Points closed (ground applied) allows the coil to charge, and points open (ground removed) allows the coil to discharge (plugs fire). Assuming power is getting to the other side of the coil.
HTH
Robin

[twincamzz]

That's what I was wondering rigidthumper. Either way, coil didn't fire so I assume this is another of them hunnerd dollar lessons for me. 

[twincamzz]

Okay, so now that I know I have to replace coil ( presently 3 ohm ), is there an advantage to replace with 4.7 ohm coil or is 3 ohm the way to go ?

[rigidthumper]

Points work better with copper core wires and 5 ohm coils.
Electric stuff likes 3 ohm coils and carbon cored plug wires.
Robin

[twincamzz]

Got a Blue Streak 4.7 ohm coil & new copper core wires on the way via the Big Brown truck. Should be here today as a matter of fact.