Let's talk spark

[Incubus]

Ok, the rejuvenation of Succubus has begun. I have an issue immediately.

I grounded the one and four plugs to the head acorn nuts while cranking the starter and then while running. This is what I found.

No.1 - strong, but intermittent spark. When it fires it's bright white/blue. It doesn't fire every time. Or even most of the time or a lot of the time, from what I can tell.

No. 4 - steady spark, but weak.

No. 1 does not fire while I crank, except every once in a while. Number 1 cylinder does not run. Pipe is cold. No. 4 cylinder runs sometimes, enough to get the pipe warm, but not hot.

Nos. two and three fire strong. Pipes very hot, very quick.

Possible causes:

1. The pickup coils, which were designed by Satan with the intention of destroying human civilization and turning us into mindless zombies feeding on each other. I think the plan is working.

2. The coil - I don't think so or I would get no spark on either side ever.

3. The spark plug wires and caps. These are new and thus far have not been considered in the diagnosis.

4. The TCI. Never understood how these work. Never intend to.

Anything else. anyone?

I am leaning strongly toward the P/U coils. I have apparently proven myself completely incapable of fixing one of these suckers, if this is the problem. I have tried numerous times and .... drum roll, please... nothing. Nada, I suck.

Does anyone have a known good set of P/U coils I can install to try to nail down the problem? They will be returned, if unnecessary. Or if you just need them back.

Thanks, y'all.

Patrick

[HobbyMan]

Check everything. do an ohm check on the coils. play with the pickup wires while cranking to see if it changes. Clean all of your connections. Also, take the TCI cover off to see if there is any corrosion in there. It can only be a certian number of items, you just need to start eliminating stuff. Actually, in stead of cranking and playing with the pickup wires while cranking, attach an ohm meter at the pickup coil connection behind the fuse panel. Move the advance and jiggle the wires. Test both pickup coils. One more thing you could do, while you have the plugs out, swap the left and right coil power wires from the TCI. If the same coil does the same thing while they are swapped, its your spark coil.

[mro]

No.1 - strong, but intermittent spark. When it fires it's bright white/blue. It doesn't fire every time. Or even most of the time or a lot of the time, from what I can tell.

No. 4 - steady spark, but weak.

Same coil...different results.
Might be a clue?


mro

[boyat68]

Succubus:

I put a new set of NGK BP-6ES in my 80G after cleaning the carbs, since 2 of the old plugs apparently were not firing correctly as cly 3&4 were colder than 1 and 2. I check out each new plug by shorting them to the case side and observing the spark. They all were good sparks. After installing the new plugs, I noticed that #1 cly was cold and had backfiring in the pipe. I knew that the plugs checked good so ignored them for the present. trying to synch the #1 and #2, but pipe kept backfiring. I swapped the 1 and 2 plug, and the cold pipe moved to #2 position. I pulled the apparently bad plug and replaced it with another good plug and both pipes started coming up to temperature. I read somewhere on the forum of someone else having problems with NGK plugs, so I will have to try using the Champion N-8Y to see if they perform better.

[planedick]

plug caps

The plug caps are resistor type and could be bad. Change them with 2 and 3 and see if the problem follows the caps. Also, you said the wires are new? You can only use the solid wire type on these because the caps are resistor type and the automotive type is resistor also and adds too much resistance.

[Incubus]

I will check the coil again, but it is already a replacement coil. I put in 3-ohm coils from some 80s vintage bike because I had issues with the spark before. It's never been solved. The plug caps are new. The wires are 7mm solid copper.

I'll try swapping plugs, and I believe I also have some other new plug caps.

I kept going back to the coils and caps the last time. I figured, then, that if it was the P/U coil then I would have no spark or at least both plugs doing the same thing, not different symptoms.

It's possible one of the replacement coils has issues. Maybe the connectors in the coil are corroded. I'll check that. I'll also try swapping the plug wires to see if it's the plugs.

It's all coming back to me now. Ugh.

I am sure this is something simple. It has to be. It always is. This is the first and only motorcycle (of my nine) that I have been unable to get to run right.

She won't win.

Patrick

[randy]

I put in 3-ohm coils from some 80s vintage bike because I had issues with the spark before.

If you're running with the ballast resistor, 3 ohms coils are no good. Stock 79F coils are 1.5 ohms + 1.5 ohms ballast for total of 3 ohms.

If you're sure the coils are 3 ohms, remove the ballast and connect the free ends of the harness together. Then see what happens.

[Renegade]

Just curious, but did you try swapping the plugs to different cylinders to verify that it isn't the plug? Or try a known good plug. I have had brand new plugs that fired perfectly fine when lying on top of the head, but when under cylinder pressure, more often than not would arc deep inside the shell rather than at the tip, causing a misfire.

If you have a plug doing that, pitch it. I have never been able to get one of those to work reliably. Even bead blasting will only make it work for a couple of minutes, then it starts tracking the insulator again.

[Incubus]

A ballast resistor. Peachy...

Thanks, Randy. According to my wiring diagram this resistor is connected to the red and white wire in line with the coils. To save me a bit of time, since my wiring harness is completely covered with electrical tape, can you tell me where this freaking ballast resistor is mounted and what it looks like?

I have a feeling.....

Patrick

[Incubus]

Never mind, Randy. I found it and bypassed it and no change. I really hoped it was that easy, but it won't be.

I didn't have a chance to work on Succubus much yesterday because it was 85 and sunny and I needed a taillight for my Honda 400 and there was one in a boneyard about 60 miles north of here. I have other running bikes. And it was 85 and sunny.

Tomorrow I will solve it.

Patrick

[Incubus]

Guys, am I correct in assuming that if the P/U coils are the issue, then I will have NO spark? Can the P/U coils cause a weak spark? Can the spark be different between the two plugs?

My current thinking is that my problem lies somewhere between the TCI and the plugs.

Patrick

[TopCatGr58]

Patrick,

I've seen posted scenarios where a person had a weak spark on 1 of the paired plugs on a coil. IIRC if it's not getting a good 12 volts then it won't generate a good field, and when it collapses it won't generate a good strong spark but a weak one. And remember, the spark travels thru 1 plug, thru the engine, and then back up thru the other plug back to the coil, but if it doesn't have enough volts, then it won't be able to jump that second plug effectively!

Yeah, usually a failing PU coil will cause problems with BOTH plugs since it controls firing of the coil which fires both plugs at the same time! But I've also read about improperly spaced PU coil gaps causing problems as well, should be 0.7mm IIRC!

As has been suggested, first try swapping the actual Plugs. Then if no change, then swap the wires. IF still no change.......hmmm?

I also read about if it doesn't have a good proper fuel air mix, it won't fire well also. Keep at it.
T.C.

[GNEPIG]

I have had ignition modules(TCI) go bad and cause this same problem.
Have you tried a known good module yet?
Sounds like you have messed around with every other aspect of this system with little or no change.

Ask Randy if he will have a look at your TCI, I bet he could fix it.
Might also be a used one at that "Bone Yard" you spoke of.
Then there is always Ebay.
Good luck

[planedick]

Still thinking

Plug caps, unscrew them off the wire end and change them to see if the problem follows.