Pamco? Coil? Plug? Wtf?

[Darylstewart]

Hey guys. First post.

Just fired up 81 Special for the first time. Completely rewired, new Pamco with Ultimate coil, new plugs, clean carbs, adjusted valves, etc.

Only one pipe gets hot. Both carbs have fuel. Both plugs get spark when held against the engine.

Switched plug wires. No change.

Switched plugs. Now the other cylinder fires, but the one the fired previously does not. Okie dokes, so maybe new plug is faulty?

Grab a couple older plugs, clean em up as best as I can. Replaced the plug that seems to have been the culprit, but still nothing.

Well WTF.

We switch plug sides, and the problem follows.

Now, we pull the good plug, mark it, and set it aside. Install another cleanish older plug. At this point, we verify all of the plug gaps.

Now we have two old plugs in the bike, one we already tried and didn't work. We fire the bike up and the old one we just out it works.

YAY! So we replace the older one that didn't work with the new one that had worked previously. Fires up, the cylinder with that new plug doesn't work now. And it switches when we swap those two plugs.

Well WTF!

Compression in both cylinders is good. If anyone has any clue as to whats going on here, please enlighten!

 

[XSLeo]

The way the coil works with a Pamco is that both plugs should fire at the same time.
So if one plug fire the other should too.
With that being said and the things you've done My best guess is the plug caps or wires may be the issue. If the caps are not installed right on the wires or the wires not in the coil right the connection maybe changing every time you remove the cap from the plug and reinstall it.
I don't know which coil you are using, so I can't say much about that. On the coil I use the wires use a metal sleeve that plugs into the coil. When you install this sleeve on the wire you need to peel the insulation back about 1/2 inch, fold it over the end then slide the metal sleeve on and crimp in place. This gives a good solid connection between the wire and sleeve.
Some coils there is a small screw down inside where the wires goes. Again peel back the insulation but spread the inner wires out in a star burst pattern. Now as you insert the wire in the coil, screw the wire down in so it threads onto the screw.
The caps hook to the wire this way.
Other than that I can't say.
Leo

 

[Darylstewart]

The way the coil works with a Pamco is that both plugs should fire at the same time.
So if one plug fire the other should too.
With that being said and the things you've done My best guess is the plug caps or wires may be the issue. If the caps are not installed right on the wires or the wires not in the coil right the connection maybe changing every time you remove the cap from the plug and reinstall it.
I don't know which coil you are using, so I can't say much about that. On the coil I use the wires use a metal sleeve that plugs into the coil. When you install this sleeve on the wire you need to peel the insulation back about 1/2 inch, fold it over the end then slide the metal sleeve on and crimp in place. This gives a good solid connection between the wire and sleeve.
Some coils there is a small screw down inside where the wires goes. Again peel back the insulation but spread the inner wires out in a star burst pattern. Now as you insert the wire in the coil, screw the wire down in so it threads onto the screw.
The caps hook to the wire this way.
Other than that I can't say.
Leo

Thanks Leo! Would you suggest splaying the wire at the cap end, as well?

 

[XSLeo]

Yes, the caps hook up as I described for the second coil option.
Leo

 

[pamcopete]

Daryl....,

You may have lost track of which of the new plugs is good and which is bad, so just replace both with two new plugs. Could be a crack in the porcelain of one of the plugs that is intermittent so just handling the plugs makes it work or not. You could also have an open in one of the plugs so it works when connected to the negative plug wire but not the positive.

 

[Darylstewart]

While that is possible, it seems to me like all the plugs work. But some work better then others, and so the better plug will fire. We were careful when we found the first plug that worked on both sides. We took it out, marked it. When it went back in, it didn't work. I guess because there was a 'better' plug in the other cylinder.

I don't know, seems like a path of least resistance thing. Totally weird.

 

[Darylstewart]

Okie dokes. The coil came with the wires attached, so I'm not ducking with that. I splayed the wires out in a star like pattern on the cap ends, tried again with the two new plugs we had and the marked plug works. It's on the 2 side. Baffling.

 

[Darylstewart]

Switched the plugs, now #1 fires.

 

[Darylstewart]

Tried a different plug on number 2. Still nothing. 1 still fires.

 

[Darylstewart]

Replaced the plug that has worked with another. Now we have two different plugs than when we started. 1 still fires, 2 does not. Pulled on the throttle a wee bit, the 2 carb popped and the bike shut off.

 

[Darylstewart]

Okie dokes. Now we tried the two plugs that have never worked. Nothing. No fire.

So, I just realized... We have two resistor plugs and two regular. We have gotten one of each to work, but not together, obviously. I'm not sure if this is a problem.

Just tried two brand new plugs, #1 fires and #2 does not.

Argh.

 

[pamcopete]

Daryl,

OK. Maybe we should go back to some basics:

1. Measure the resistance from one spark plug cap to the other. Should be about 25K Ohms.
2. How are you determining when a plug fires or not? If you are using a timing light, then the coil produces a positive voltage on one of the spark plug wires and a negative voltage on the other. Some timing lights will not work on the positive voltage, or only work sporadically.
3. Check the voltage on the coil and the red wire going to the PAMCO. Should be slightly less than battery voltage.
4. Are you using the kick starter or the starter motor?
5. Do not use both a resistor spark plug and a resistor cap. One or the other.

 

[Darylstewart]

Okie dokes, just as you sent that we finished testing the coil. 25,000 ohms. Coil checks out.

We are now using non resister plugs and whatever came from miles xs in the package with the dual output coil. Voltage on coil measures .07 lower than battery.

We are using kick starter only.

We spun the pamco plate by hand and saw appropriate spark.

And we know the plugs are firing because we've pulled whichever hasn't been firing in the engine and watched it spark while holding it against the engine.

 

[Darylstewart]

I wonder if we had a bad ground..?

 

[pamcopete]

Okie dokes, just as you sent that we finished testing the coil. 25,000 ohms. Coil checks out.

We are now using non resister plugs and whatever came from miles xs in the package with the dual output coil. Voltage on coil measures .07 lower than battery.

We are using kick starter only.

We spun the pamco plate by hand and saw appropriate spark.

And we know the plugs are firing because we've pulled whichever hasn't been firing in the engine and watched it spark while holding it against the engine.

OK. So you don't really know if it is the ignition or carbs? When you previously said that the cylinder wasn't firing, you then checked the spark plug out of the engine and you got spark? I think you should look for something other than the ignition.

 

[Darylstewart]

Yeah, it's def not the ignition. We knew that.

So, we got it going. Helluva lot of backfiring going on, but going. We cleaned up our grounds and vented our makeshift gas funnel tank thing. I think it was the grounds.

Anyway, that was entertaining. Thanks fellas.