Part II, No Spark

swagsherman

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Hello, it's Wendy again. Now, no spark. Let me explain what I've done and why. Seems like it's something stupid I'm missing again.

Once we got her to charge (thank you again!), still could only start with kickstarter (no electric start). Tested wires and found continuity from button to the connection inside headlight bucket. Also had a mess from the previous owner. He wired in a fuse box and one inline fuse (instead of a 4-fuse box) using different gauge wires. So, my thought was to just replace the wiring harness, take care of green wire problem from before, clean up fuse box, and likely solve push-button start problem.

Plenty of magnetic field after installing new harness (from Mikes XS). However, no spark now, no brake light, no signal lights. I removed the old while installing the new (as opposed to pulling the old one out completely, then starting over with new). All connections seem good. Stator is new (with new wires as well).

Again, seems like some really stupid small error, with big consequences. Always had spark before I attempted to clean things up. What/how should I test things? What/how should I look at?
 
Forgot to add this is an 81 XS650, TCI ignition. All stock. Went back through all connections. Looked good. Did find a connection in headlight bucket that looks like it goes to tachometer, where the wires in the Mikes XS harness were flipped -blue lined up with black and black with blue. Swapped those and still same issues - no spark, no horn, no signals, no brake light. Fuses all look good. I'm lost. This should have been an easy swap, I thought.
 
So... now we know you're a glutton for (electrical) punishment. ;)
Lets start with the TCI box underneath the battery box. Ignition on, kill switch to run... check for 12V on the R/W (red/white) wire. While you're there, make sure the black is a solid ground... less than 1 ohm.
 
Here's the diagram we're gonna work off of.

81_ XS650H_SH.PNG
 
Can't wait to stop drinking to try it the wiring diagram. Exciting!

Oh no! It’s easier after you’ve had a few drinks!
902C7374-170A-44F3-8936-2DAFE85E2899.jpeg

Seriously, it seems intimidating at first, but just stick with it. If you’re not very experienced with wiring ( as I was not ) it seems a little overwhelming , but It slowly starts making sense.
 
Ok - I have stopped drinking (for now). Battery voltage 12.8 v; R/W wire is at 42.6 mV??? R/W wire at coil is 41.3 mV. Yikes. Ground 0 ohms. What does all this mean, great wise one? Are you going to try to make me read that damn diagram? What am I doing wrong this time?
 

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I usually find those mV values correspond to the power being on but none getting through to the wire you are testing. It would seem to me that there is no power on the R/W ignition line. Is there voltage at the main fuse (20A) in the fuse box? If answer is yes then check voltage at Ignition fuse in fuse box (10A). If yes then trace voltage to the Kill switch and then on to the coils etc.
 
R/W wire is at 42.6 mV??? R/W wire at coil is 41.3 mV
Gah... damned auto ranging meters.... hate 'em. Mini-rant over.
Means you got nuttin'.... More specifically, that's .042V... almost nothing. So now we follow the yellow brick road 'till we find the problem.
Follow the R/W wire... it goes to the kill switch. Connector's in the headlight bucket. There's 2 R/W's there. One is 12V from the fuse, the other goes to the TCI box and the coil. See if you have 12V on one of 'em.
 
A wiring diagram can be intimidating to look at as a whole. Good thing is you don't usually look at the whole thing to find a problem
On the diagram, start at the battery. A red wire goes from there to the main fuse and switch. From the main fuse it feeds the other fuses. as well as other things. Don't worry about the other things.
One of the fuses is the ignition. This has red/white wires. It runs from the fuse to the engine stop switch. From the engine stop switch to the TCI box and the coil. It also goes the safety relay.
So if you use your meter and follow the diagram you can test for voltage at each step of the diagram
It shows the connectors. Most are in the headlight bucket. Main switch is the wire bundle with red, brown and a blue wire.
Probe the red lead into the wire side of the plugs to touch the bare metal of the connector. You can probe both sides of each wire. This will let you know if the plug has issues. Then along the diagram you find the engine stop switch. This is a wire bundle I the bucket that has two red/white wires and a blue/white wire. The two R/W are the stop switch wires. The B/W is the start button. Probe both sides of this connectors r/w wires.
Now following the diagram next you come to the TCI box and coil. The TCI plug is under the under the plastic side cover. The coil Under the tank. TCI box has 7 wires. Probe the r/w wire on both sides of the plug. The coil has a r/w and orange wire. Probe the r/w wire.
At these places you should get near battery voltage. The orange wire on the coil may have battery voltage or nearly zero volts. The TCI uses the orange wire to control current flow through the coil. When the TCI grounds the coil till it gets a signal from the pick ups. This signal tells the TCI unit when ti fire the plug. It then ungrounds the orange wire to cause the coil to spark. When the coil is grounded the orange wire voltage will be near zero. When ungrounded it will be near battery voltage.
Some where along this pathway you will find you lost the voltage. The issue is the thing just before you lost the voltage.
Ok an example might be like you get to the wires at the stop switch. No power on either side. This means the issue is between there and the last place you had voltage. Most often a poor connection at the connectors. Another is dirty switches.
You can trace every circuit on the bike this way. With a bit of practice you will find it much less intimidating to look at a wiring diagram.
Leo
 
0.042 V at one R/W wire; nothing on the other (when new harness is disconnected from handlebar switch wires). 0.042 V at each R/W wire (when harness is connected).
So... no power to the kill switch. Follow the yellow brick road... ;) Wire goes to the fuse block. Fuse Good? Power at the fuse?
 
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Your problem is likely the next item upstream of where you are. Tracing the diagram backwards from the stop switch. You find what? This leads back to the fuse box right? Then test for voltage at the fuses. The fuse marked ignition or if no markings the one with r/w wires. Does it have good voltage on both ends of the fuse?
Leo
 
Yes - no power on either side of ignition fuse. Power at positive brush, power at reg/rec (look, I'm learnable - and obviously tried to trace brown wire through spaghetti model). Other three fuses power on both sides with key on.
 
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