'80 SP Electrical issues

[Swedemoto]

I have an '80 SP new to me, with Dyna III ignition. I just replaced the alt. rotor, adjustable regulator, and rectifier. Left cylinder has been running rich. Choke cables are new and have been backed off. New carb rebuild kit, and floats reset.
Valves adjusted as well, they were pretty much on. Compression is over 150 for both sides. A friend (Harley tech for 20yrs), is helping. We haven't verified timing yet.
The bike would run but felt lagging even at higher revs. A couple times it would just die while idling for too long, then not restart.
Now carbs are sync'd better, not by vacuometer, and throttle response is crisp. Trying to sync carbs per manual, we pull the left side plug and the bike barely drops in revs and still idles. It does smooth out when re-connected, but barely.
If we pull the right side, it dies immediately. Ive read a bit of guzziology, is this pointing towards coils and or plug caps?
I can't think of what else this could be. 

[fotoguzzi]

if you still have those old metal plug caps, relocate them to trash bin and get some NGK caps. check that leads are making nice connection on both ends.yes could suspect a coil.
 is that plug firing?

[Swedemoto]

coils look to be original, haven't verified and it's not here to check. It has NGK caps already. Just wondering if they may have failed. I'm researching coils and new wires/caps now. The left coil does feel hotter and feels slightly "tingly" to the backs of fingers.

[Chuck in Indiana]

coils look to be original, haven't verified and it's not here to check. It has NGK caps already. Just wondering if they may have failed. I'm researching coils and new wires/caps now. The left coil does feel hotter and feels slightly "tingly" to the backs of fingers.

For whatever reason, my old SP started "eating" coils. I eventually ran a dedicated wire from the points to the coils and that fixed it.

[BMCMOTO]

In my opinion the NGK resistor cap's failure mode is to go what I call semi-open.  In real terms they seem to work well at passing energy at higher RPM levels but as RPMs drop and energy diminishes they fail to pass the lower energy.  Check the resistance, if other than 5k ohms replace.  Rough uneven running at idle while performing well at higher speeds is the hallmark failure in my experience.  I usually change them once a year or if I have difficulty maintaining an even idle.  It can make balancing throttles at idle a real pain, balance fine at speed but not at idle, loose timing chain can show the same difficulty but is easily seen as timing marks that jump all over the place.  I am not sure how the Dyna ignition is affected, it is most obvious on points bikes but also happens to fuel injected bikes as well.  I have even replaced some that check OK, this is where an old Sun Scope would be useful, watching the spark pattern was the best way to diagnose many things.   YMMV

Brian

[Idontwantapickle]

Swap the coils, just switch the wires from the distributor and the HT leads. See if the problem move as well.  If not its the carbs.  It's pretty easy to get the carbs in a state where the slide is too high at idle and the idle mixture adjustment gets vague and rich.

[rodekyll]

What do you mean by "the timing has not been verified'?

[Swedemoto]

I don't know that he checked the timing, he may have. He knows that should be verified before adjusting the carbs. He's had it for a few days and I've not been there the whole time. I'm trying to get up there today.

[rodekyll]

There are two sets of pickups for the dynaIII and they both need to be set before it makes sense to try any of the other adjustments.

[Swedemoto]

OK, We'll check that thanks! I have the Dyna instructions to get to him.

[Kiwi_Roy]

When it is running do both header pipes / cylinders get hot?

Did you do anything like remove the distributor?

[Swedemoto]

Both sides heat up equally and exhaust pressure seems equal as well. Did not remove the distributor.

[Groover]

I think someone had a similar issue like this and it ended up being a bad/hardened seal on the choke plunger. Maybe check those. At least try swapping the plunger from one side to the other and see if the issue moves with it.

Good luck.

[fotoguzzi]

just wondering how you feed the carbs.. do you.. 1, have a crossover in the line or.. 2, are you running to the carb direct/separate from each of the petcocks? if 2 then could be a flow problem?

[Kiwi_Roy]

Now carbs are sync'd better, not by vacuometer, and throttle response is crisp. Trying to sync carbs per manual, we pull the left side plug and the bike barely drops in revs and still idles. It does smooth out when re-connected, but barely.
If we pull the right side, it dies immediately. 
I can't think of what else this could be.

Reading back over this it's obvious that the carbs aren't synced properly, the right side is doing all the work.
Do a quick sync with a drill bit under the slides.

I had something similar happen to my California II, It would idle fine but no power, I found one of the cables had come unhooked in the throttle twist grip

[rodekyll]

folks -- the timing has not been set.  I asked, he said no, and he didn't take the hint.  Apparently a 20-year HD wrench doesn't think you do that with a dyna.  Or maybe he's 20 years old and a HD mechanic.  Either way, until we know he's got that most essential baseline set, why are we discussing fuel?  Until the OP can tell us about the timing this discussion is a waste of time.

[hudson]

While you are investigating the timing...  Here is some quick simple tests to check off your list.

Do an ohm test on your SP cables with a multimeter.  Setting around 20 ohm, positive in one side, negative lead on the other.  As you check the reading , bend some wire to make sure it doesn't short out.  Usually averages 5-8K per foot, dependent on cable length.

While you're at it, do the same test on the coils for primary and secondary.  Check manual for specs but I think it should be around 3-5 ohms.