Help guys! Electrical problem that's boggling my mind!

[Pattymatts]

Howdy guys!

First off id like to say thank you to anyone that posts on here and that can give me some insight. Okay so here's the lead up to this gripe. My bike was delivered from a cross-country freight last week, I was trying to kick her over because she'd been sitting for a bit and nothing, but every time I'd cut the ignition off I would here a sort of "poof", now I thought it was odd but kept going at it and eventually Lucy fired up. But it seemed the right cylinder wasn't doing too hot at all and after about 30 seconds she croaked. So you know, men take the path of least resistance, just like electricity, right!? I thought maybe she needed some new plugs. Replaced the plugs, and again, nothing. Took the plugs out one by one, grounded them on the case and gave her a few kicks, but the plugs just weren't lighting up. But here's the kicker, when I flipped my ignition OFF (single throw switch, no key), the plugs lit up(just once). Now a lightbulb went off and my dumbass brain said, "Ohhhh those 'poofs' were mini backfires!" Now I'm an aviation electrician with a few years experience, but I can't wrap my head around this gripe. Probably because it's a motorcycle and not a jet haha. But my electrician brain is calling out the coils or the switch. Please help, and thank you!

 

[jmink427]

Sounds like when you turn the power of the coils are firing... I would check the points if it has any make sure the contacts are breaking that is when it will make the coil fire... So basically if your points aren't breaking you have power to them all the time... When you turn the switch off it is acting like the points breaking and making the coils fore one time when they discharge.....just a thought..

 

[jmink427]

Sounds like when you turn the power of the coils they are firing... I would check the points if it has any. make sure the contacts are breaking that is when it will make the coil fire... So basically if your points aren't breaking you have power to them all the time... When you turn the switch off it is acting like the points breaking and making the coils fore one time when they discharge.....just a thought..

 

[Pattymatts]

Apologies I should have specified, it's an '81. No points ignition unless I'm not picking up what you're throwing down.

 

[jmink427]

Electronic ignition then.... Check the pickup for the ignition and make sure there is no corrosion or rust on it and may not be trigging or the transistors could be shorted giving constant voltage on the coils .. All coils works the same way when you break the circuit to the primary side it produces the high voltage on the secondary side and makes the spark...

 

[fredintoon]

Hi Patty,
there's a clue when you say - - - when I flipped my ignition OFF (single throw switch, no key), the plugs lit up(just once) - - -
The stock ignition works with a keyed switch.
The dreaded PO has meddled with the wiring by fitting an extra switch and has got it wrong.
Best I can advise is compare the wiring you have with the wiring diagram, see what's been done to it and put it right.

 

[XSLeo]

Even with a key switch an electronic ignition will spark once more when you turn it off. My 81 does it, the Pamco in the 75 does it, my 03 Harley does it.
With power on, power flows to the coils. The ignition just grounds the coils to let the power flow through the coils, this creates a large magnetic field in the coil. When the ignition decides when to fire the plugs it stops the power flow through the coil. This allows the magnetic field collapse, this creates the current flow in the secondary side of the coil that jumps the spark.
The TCI on your 81 uses a set of pickups on the stator, these pickups sense the passing of a magnet in the rotor to tell the engine position. It uses this info to determine when to spark.
If the pickups are bad, testing procedures and specs are in your repair manual, The TCI won't know when to spark.
Another thing to ch4eck is the voltage on the red/white wire at the TCI box. If low or no voltage the TCI won't work even though power is going to the coil.
In the repair manual is a section on testing the ignition. Follow the steps. This will help you determine what's wrong.
Leo

 

[Pattymatts]

fredintoon, my bike was chopped on the west coast while I was deployed. It is kick start only and the man that built it and wired my bike cooked up a custom electronics box, and apparently had no where to put the keyed ignition so instead installed a master switch. He also had the bright idea of putting the only access to this box in the rear, where I have to disassemble the whole rear end to have access to it.

XSLeo, even if the elctronic ignition has been thrown out and the bike has been modified to kick start only will the plugs still spark once as the ignition switch is turned off? I apologize of my lack of knowledge to all. In the words of Joe Dirt, "I'm new! I don't know what to do!"

 

[XSLeo]

You need an ignition. Stock or aftermarket. It won't run with out one.
The staring system, kick or electric has nothing to do with the ignition. All they do is spin the engine.
An ignition system causes the spark at the right time for the engine to run.
Contact the builder and get a copy of the wiring diagram he used to wire the bike. There are some checks you can do to determine what ignition you have. On the left side remove the round cover that says Yamaha on it.
If it looks like this pic then it has the stock ignition. Notice the black oval in the upper right side. This is the stock TCI pickup. The TCI uses it to determine engine position and rpm.
Leo

 

[XSLeo]

On the top of the engine remove the round covers on each side of the head. I have pics of the left side but none of the right.
If it looks like this, you have a Pamco ignition.
In this pic you see the Pamco rotor and sensor plate.
Leo

 

[fredintoon]

Alternatively, if there's nothin' under the cam-end covers you got post '79 ignition like in Leo's post #9.
Or, if there's points under one cover and a centrifugal advance mechanism under t'other you got pre '80 ignition.
And if you'd attached a photo and said what year the bike is, it wouldn't have taken 11 posts to get this far.

 

[Pattymatts]

Thank you for the information, XSLeo. And yes it is a TCI ignition. I have contacted the builder for the schematic he used while wiring.

And fredintoon, if you would have read the posts, you would have read that I apologized for not specifying the year, and then say what year the bike is in the same post. Which is post #4 by the way. There's no need to be condescending. But thank you for your help.

 

[fredintoon]

Thing is, XS650 parts can be swapped from year to year like LEGO
Any of your bike's POs could have changed it's stock ignition for a PMA/Pamco system or for the earlier points system.
While each of these systems will work just fine, their fault analysis is completely different.
And as you say the bike has had a major rewire anything is possible.

 

[XSLeo]

Ok, With the stock TCI there should be a black box somewhere. Being an 81 it should have 6 wires. Black/white, black, two red/whites, green/white and orange.
Three of these go to the pick ups. the B/W, G/W and one of the R/W's. The black is ground, the other R/W is power in. Orange goes to the coil.
You don't mention if you are running a battery but if it poofs when the switch turns off I assume it has one.
Now with it sparking when the switch is turned off the coil should be ok and you are getting power to the coil. You need to check the voltage of this power. Use a multimeter on a DC scale, digital will be 20 volt scale. with the key on check voltage at the battery, this is your source voltage, the voltage tests you do compare to this voltage. Now test the voltage on the red/white wires at the coil and TCI box. Both should read the same as or within .2 or.3 volts, much lower you have a bad connection or switch somewhere.
The TCI has power going to the coil and TCI box, the coil needs power to spark, the TCI needs it to power the internal parts. The TCI receives signals from the pickups, the TCI uses these signals to determine crank position and rpms. It uses this info to determine when to spark. The TCI uses a transistor to carry the current the coil needs just like points do. When the transistor is "on" current flows, when "off' no current.
When you turn on the switch power flows to the coil on the R/W wire, from the coil to the TCI box on the orange, inside the TCI box the transistor is "on" this lets current flow in the coil. When the TCI box determines the coil should spark it turns the transistor "off" This makes the coil spark.
Now when you turn the power of it does the same thing as turning the transistor off, plugs spark.
Now your issue could be several things. Power to the TCI box, faulty TCI box, the pickups. Your repair manual has a section covering how to test the TCI system.
Your TCI box is at what is referred to as end of life. It could crap out at any time, maybe today maybe ten years from now. We have had some luck fixing the TCI boxes. Some have got them working by just resoldering all the solder joints on the circuit board inside. others replace parts.
If the resoldering didn't help I might replace it with a Pamco.
Changing parts has worked but you may mess with it a lot before you replace the right part.
Do these checks, write down the results and report back.
Leo