I just had a weak/no spark problem on my '94 FXSTC.
I installed a new Harley OEM coil.
It made it 8 miles before it died.
The bike was having problems with cutting out but I just thought that was the new carb not set up right yet (I need to fine tune it).

Here's the question:
What could eat a coil in 8 miles?????

 

Not likely. Heat and age is what usually leads to coil failure. A dead short or something would have been apparent from the get go. It is possible to get a defect that had poor insulation though.

Pull the coil from your other bike and hook it up temporarily to see what happens.

I am kind of leaning towards a bad pick up being the problem. Either that or the ignition module. Heat and age is the enemy of ignition modules.

Maybe loose connections?

Is there a tachometer on the bike? If so, disconnect it to see if it makes a difference.

 

I used to have a car that did that, when it got hot the coil would short out. When it would cool down I could drive it again. Couldn't test it unless it was hot and failing.

Good luck sometimes that stuff can be miserable to diagnose.

 

Are you sure it's the coil? If so and If it's the primary side of the coil I would suspect a voltage issue... Or the new coil is just a piece of crap... Sorry to hear man...

 

See above.

 

What did it turn out to be on your car??

 

Ignition module went **** up on my Ford 5.0L in my Jeep CJ. Took a couple of days to diagnose it, and an hour or so to replace it (have to tear the distributor apart). Fired right up afterwards.

Anyways... I'm watching to see what actually is the fault.

 

It was the coil, I got to the point where I carried water to pour over it to cool it down. New coil worked for me.

 

harley sells 3 different OHM resistance coils -- 1.5 < wrong one - 5.0 wrong one - 3.0 ohm is the one you should have

 

I've a friend with an EVO that had a new ignition module go bad on him within a year.