Yes - I still have an electrical problem!!!

[Keithh]

Greetings all,

Unfortuanately my electrical gremlin is still with me - the bike starts and runs great one time, and the next time - no spark! I put on a replacement harness, new battery and very time I check voltages, etc., everything appears to be normal. The only thing that may be malfunctioning is the resistor - is it supposed to drop voltage to the coils after starting? It doesn't - stays the same. It is both coils not firing, so whatever it is must be common to both. When it decides to run, it runs great.

When it is being a pain, the only time you get a spark is after to try to start it and then turn the handleber switch to off, and you get a spark. Once it backfired and sounded like a shotgun - had the neighbors running!

My next step is to basically rewire the ignition portion and eliminate all the unneeded stuff and see what happens!

Any thoughts appreciated - the guys in the funny coats are gaining on me fast!!

Regards
Keith

[crazy steve]

First thing, the resistor will show the same drop all the time. It gets bypassed by the TCI when starting (increasing voltage to the coils).

Next, you've still got a poor connection somewhere. It sounds like your handlebar kill switch is dirty (a common problem), you need to remove/clean that. Finding voltage at various places doesn't mean you don't have bad connections, look here....

http://www.xs11.com/forum/showthread.php?t=35339

[BigRed]

+1 for cleaning your kill switch. If moving the switch fixes your problem, it's probably in there.

Also, you could be getting low voltage to your coils through bad connections and bad grounds. I had a bad ground at my voltage regulator that was costing something like three volts. I think 10.5V is the cut off where the TCI won't fire the coils.

[GLoweVA]

Keith, you have a 78/79. So you should have the kickstart option.
How about trying to kick start the bike?
If it restarts every time with the kickstarter then that's a data point in this troubleshooting process.
This way it'll tell us that it might be the 'starting' side of the house and the coils/ballast resitor/TCI is what's the culprit.
Looking at the wiring diagram, (steve can confirm or correct me if I wrong)
the starter relay is what supplies the juice to the coils, thus bypassing the resistor and thus supposed to give the coils the max juice.
If you kickstart, then the starter relay isn't in play and if she starts every time then we have a better idea of where to look.
(plus what BigRed said about battery drain, maybe the starter is dropping the system down enough, again with the kickstarter then you'll have no drain from the starter)

I'm not doing anything this weekend, I can swing by whenever Sat/Sun and maybe help you figure this thing out once and for all.
(I'm fairly savvy with wires and troubleshooting issues, but my knowledge of the 78/79's isn't as good seeing I've got an 80.)

[TopCatGr58]

Hey Keith,

As has been stated, the B.R. drops the voltage to ~9 volts once the engine is running....to not overheat the coils. If the coils are seeing 12 volts all the time, then the BR may have shorted across...a bit rare..they usually crack and break apart providing no continuity and therefore no power for running...but the symptoms in this situation are it will start because the TCI bypasses it, but once it's actually running, the TCI routes thru the BR, but it can't get thru, engine dies!

IF you've run your bike for any length of time with the full 12 volts going to the coils...you may have fried your ignition coils! Folks can bypass the BR just for starting diagnostics....and If the bike starts and runs with it bypassed, but not in circuit, then they know the BR is bad and can replace it. But folks are not to run their bikes for very long with the BR bypassed because it will fry the coils at full 12 volts for very long!

Yours doesn't sound like this scenario. Unplug the BR and test it's resistance on the 2 wires of the plug....should be 1.5 ohms...if much less or non, then you may have found part of the problem. Still sounds like the kill switch corrosion....HOWEVER, I just retested mine, and with the kill switch in the OFF position, my bike won't start or engage at all, so I'm not totally convinced but then again my bike is an 81SH, don't know if the circuitry is different for the earlier models that would allow the starter to engage and turn the engine over, but prevent power from going to the TCI??

When it won't start, have you checked for presence of 12 volts going to the coils. IS the restarting problem more prevalent after the bike has been running for a while, or just a new day and cold start??

Hey George, if you'll be that close, then drop on by here as well for some in person fitting measurements and such!!

T.C.

[Keithh]

Thanks Guys - all good tips to pursue. Regarding the ballast resistor, it was showing 12+ volts at the coils after the engine was running for awhile as I balanced the carbs. Another data point - I disconnected the main plug from the TCI and the red/white and orange and gray from the coils. With one lead from the ohm meter grounded to the frame, I checked the red/white wire at the plug for the TCI and I got a continuity reading between the red/white and the frame. It stopped when I pulled the connection to the fuse box for the ignition. A check of the fuse box showed continuity from the box spade connector and the frame. Seems weird - I'm wondering if an obscure ground is lurking somewhere. More checking tomorrow!

Cheers!

Keith

[Lamric]

Check out the resistances of the pickups from the TCI connectors, failure of one pickup can take out both coils.