Weak spark

[ZombiePotatoSalad]

What is voltage at this same point when cranking?

Hard to tell, it jumps around. Let me see if I can attach a video

[OldVet66]

Don't worry about measuring anything through the coil you have 12.33 volts there and nothing happens until the circuit is interrupted. The collapsing field is what generates the spark. Use any wire that is capable of handling 12 volts. A half a piece of lamp cord would work. You will see there is a smooth edge on the side of the cord and a ribbed side indicating hot and neutral. My last question might be important so it would be good to answer that before trying to do the test.

[ZombiePotatoSalad]

You wouldn't believe the problem... the coils I got, one set of them had the stuff inside the cap installed backwards.

EDIT: Maybe not that easy. I got cylinder 1 to spark, but 4 wouldn't. Now 1 won't. I replaced the caps for 1 and 4 with NGK caps I got for a previous ignition coil. Still no spark, but the copper screw inside one of the caps that came with the new coils broke.

When I put the probes in the caps, I now see 1.28 with the new caps on when cranking.

[ZombiePotatoSalad]

What is your question?

[OldVet66]

What is the voltage when measuring from the coils to the motor case near the starter motor.

[ZombiePotatoSalad]

From where on the coils?

From the orange/white wire to the casing, it jumps around, topping out at about 6.47 while On, then goes back down.

Does it matter how much copper wire is in the bullet connector? It reaches to the end of the bullet terminal. Should I crimp the terminal and connector on the wire strands, or the wire casing?

[OldVet66]

On the wire strands. If you crimp it to the insulation (casing) you will not have a connection. Some bullet connectors (wing type) crimp into the wire strands and clamp around the insulation for extra support, but it takes a special crimper like they used at the factory. First you measured 12.33 volts. If you measured from where you made that reading, to the motor case and got 6.47 volts on the same meter scale it means you have a very bad main ground from the battery to the motor case which is where the starter motor gets it's ground. That would explain your voltage drop when you crank the bike. It also makes the starter pull a lot more current, not good.

[ZombiePotatoSalad]

It seems to jump around a lot, and not really stay consistent.

So how would I fix that?

[OldVet66]

You are probably not getting a good contact with your meter probes. Your DC scale should be about twice the voltage you are reading or as close as possible. look for where the main ground from the battery is bolted to the motor case and clean that area for a good contact and read the orange/white wire where you got 12.33 volts. If contact is good it should give a steady reading. Wouldn't hurt to clean the probes also.

[ZombiePotatoSalad]

I hooked up Coil 2's bullet connectors (which were the original ones that came on the coils) to the wires that go from the harness to Coil 1. No spark.

It may be the connection between them. Coil 1 doesn't have the original bullet connectors anymore, neither does the wiring harness. They don't seem to like anything except the original bullet connectors. Modern bullet connectors, spade connectors, nothing seems to work.

[OldVet66]

You are trying to do too many things at the same time and confusing yourself. Track down your voltage drop problem first because nothing is going to work properly until that is solved, and if it persists you may cause further damage to the bike. I do not know if your coils, caps or ignighter are any good, but I do know one thing for sure. None of it is going to work well or at all with the voltage drop you have described. You are trying to solve a problem with at least four variables and you haven't nailed down one for sure yet before you try something else. It is frustrating for me, everyone else and especially you. Diagnosing a problem over the internet is very difficult. Please take one step at a time. That way things will eventually start to fall into place.

[ZombiePotatoSalad]

I'm just wondering why it affects one coil, but not the other. Shouldn't they both be affected?

Alright, all power flows from the battery, so I'll start there. You mentioned the battery ground wire that runs to the casing. I found that. It's solidly connected. However, there appears to be some rust on it. Should I clean that off?

[OldVet66]

Clean it just enough to get a good contact for the negative meter lead, then read to the point on the orange/white wire where you had gotten a reading of 12.33 volts. The coils can be dealt with later. That cable from battery negative to the motor case provides the main ground for your starter motor and the rest of the bike frame.

[ZombiePotatoSalad]

Ok. The only issue is I can't remove the plastic airbox to get at the ground screw, the screws holding it on are rusted. I scrubbed it with a metal bristle brush. Also cleaned around and under the battery box as best I could.

[tom203]

Ok. The only issue is I can't remove the plastic airbox to get at the ground screw, the screws holding it on are rusted. I scrubbed it with a metal bristle brush. Also cleaned around and under the battery box as best I could.

This main ground wire....is it attached to motor with a hex headed bolt? Can't you get at it with six point wrench or maybe a vicegrip if it's rusted solid ?