Tci readings

[Keithh]

Hello again!

Once again after several days of cooperating, the possessed bike decided not to again yesterday - this isn't even funny anymore! Well, maybe a little; I think the bike is getting a good laugh!

To help with my troubleshooting, I was wondering if anyone can tell me what the readings should be at the bigger TCI plug. While messing around with it last night, I checked the connector for grounds. With the key off, it appeared that every wire had continuity to ground except the emergency stop switch, which was open as it should be. When I unplugged the fuse for the ignition, most of the wires where no longer grounded. This may be normal, but I figured I would as nothing else seems to make a difference.

Also, I noticed that when testing the orange and grey wires at the coils while trying to start it, the orange showed a voltage of 11+ volts. The grey one nosed dived to 1-2 volts. That clearly doesn't seem right.

I'll do more snooping tonight, hopefully armed with wisdom provided by you folks!

Thanks for your continued support!

Keith

[crazy steve]

There have been reported cases of the solder joints inside the TCI unit breaking, causing intermittent operation. These can be repaired, but getting the unit open is a bit tricky. I haven't done this, maybe DaVinci will chime in...

[DAVINCI]

Yes, I have done MANY of these. it's not hard work, but if you've never soldered, you could do more damage. I'll see if I can find my pinout diagram and post it. BTW, you don't mention what year / model bike you've got. I only have diagrams for E, F and G models.

[DAVINCI]

OK, here you go. It's a little fuzzy, sorry

[GLoweVA]

Keith has a 79F standard.
I've been keeping tabs on his issues to help and I have this wiring drawing that should help a little.

Just to clearify something, there are 2 R/W wires to the TCI.
One diagram show one of these to be W/R, but then turns to R/W.
The first (R/W) wire, (next to the black wire in the plug) is the power in.
This one is the one that needs the 10.5V to run.
The other (R/W) (next to the Grey) is the one that feeds the coils to bypass the ballast resistor.
It gets it's voltage from the R/Y wire (from the starter solenoid) during starting (~12V) and when the bike is running it comes from the other R/W wire, this will only see ~9V due to the ballast resistor dropping some of the voltage.
Here's a pic of the circuit.

If the grey one dived to 1-2 volts, it sounds like Davinci and Steve said there may be a solder joint in the TCI that is intermittent thus causing your intermittent starting issues.

I can't seem to recall my eletrical theory, but isn't there a way you can test continuity thru that transistor?
But then, doesn't the power come via the R/Y thru the diode to the R/W to the coil then to the transistor via the Grey (G) wire. So if you're seeing 1-2 volts there, then it looks like there may be an open in the coil wire (or the coil).

Keith, sorry I've been so busy at work. I even have to work this Sat too. Maybe Sunday, I might be able to swing by and maybe even try to get TC to come by with his spare TCI, if not, I can 'borrow' the one off my SG to try. It has the same part number, so it should work.

[DAVINCI]

What's really happening inside the TCI?

Power is fed directly from the battery into the ignition coil, then the ground leg is switched on and off by the transistor in the TCI.

Here are the solder joints that go bad...



The two on the left are the coil connectors.

[Keithh]

Thanks Guys - great info to know (I still like breaker points! )
The bike behaves the same way even with a know good TCI in place. It has me wondering if there is a ground someplace that is intermittent.

Leads to another question: What components are actually needed to make the engine start/run? It seems like most of the components in the electrical system can be removed with out effecting the ignition circuit. I'm going to start isolating parts of the system to see if it clears the problem - at least then the search well be focused - I hope!

George - no worries - I've been too busy to devote a lot of time to it as well. If I can't get this sorted, we'll work out a time.

Keith

[DAVINCI]

How do you know your problem is not fuel related?

[Keithh]

I have a spark plug out and visible as I crank the engine (or kick) over - no spark. It will make a spark if after you crank it over, you put the handlebar switch to off - it gives one spark. One time it gave a backfire that sounded like a shotgun - had the neighbors running for cover! It has been doing this for a long time. No wonder the PO gave up on it!

[BA80]

There's a clue Keith. Sounds like you may hav a bad kill switch.

[TopCatGr58]

Hey George,

I dropped off my spare 79SF TCI last weekend, so he's got it already. He says that he swapped it out while the bike was in it's RUNNING state, and it worked as well as his OEM unit. What I haven't seen him say with certainty is that WHEN the bike isn't wanting to start, whether he tried swapping in my TCI and if it still didn't start???

Davinci, we took the cover off of his OEM TCI and the solder joints looked good and shiny, same for the spare unit from my bike.

I can't recall if Keith has inspected the PU coil wires, or tried wiggling them when it's not starting to see if anything would change??

T.C.

PS....after seeing Greg's post, the other item I was thinking of is the TIP OVER switch, it can be unplugged to bypass it. JAT!

[Keithh]

TCI /Starting Update

Greetings once again. Thanks for all the advise that piled in today to my quest for help (and sanity - although that may be overrated). I did some basic troubleshooting - disconnect one component/circuit at a time to see if something cleared the problem. Nothing did until the bitter end when I unplugged the rectifier/regulator - started up! So now I think I have some idea. I plugged the regulator back in - and it still started up! One by One I added pieces back into the system and the bike continues to start. Not sure just what happened when the regulator was unplugged that allowed it to start - more baffling is that when put back in the system, the bike continued to start. Leaves me with an uneasy feeling that this adventure may not yet be over.

And they wonder why I drink....

Always open to more thoughts!

Keith

[XS1100 Newbie]

Sounds like it is time to go through every connection on the bike and clean and reassemble with dielectric grease.

[natemoen]

Sounds like an intermittent connection somewhere and you messing with the wiring caused a failure and reconnection.

[GLoweVA]

Nothing did until the bitter end when I unplugged the rectifier/regulator - started up! So now I think I have some idea. I plugged the regulator back in - and it still started up! One by One I added pieces back into the system and the bike continues to start. Not sure just what happened when the regulator was unplugged that allowed it to start - more baffling is that when put back in the system, the bike continued to start.

It sounds like the 'bad' connection was there at the regulator/rectifier.
Maybe the connector/wires had a 'little' short to ground causing your voltage of the system to drop enough at the TCI so no spark.
The Reg/Rect is in the circuit as soon as the key gets turned on, so that might be it.
I'd concentrate on cleaning/inspecting that particular connection.
If I recall, you've got a different(replacement) harness, so that is probably okay, so I'd check the connector/wires to the reg/rect. (those haven't been replaced)
At least now, it it does act up again, you have a point to start troubleshooting again.
In other words, next time it doesn't start, try pulling that one connection and if it works, bam! there it is.