82 KZ550LTD, Electrical start problem

Hey forum,
Went out to the bike ('82 KZ550 LTD) this morning and it won't start - as in, no sound whatsoever when I push the start button.  I've checked the battery (good), the fuses (look fine, and good continuity), the clutch start cancel switch (good continuity).  I'm getting headlights/brake lights/turn signals/horn just fine.  I haven't checked the engine on/off switch yet, but it's in the run position.

My next step was to check the starter solenoid.  The Clymer manual states "check for battery voltage at the black wire to the solenoid when the starter button is pushed."

I don't have colored caps, but I'm assuming "red" is the battery wire and "black" is the one that leads to the starter.  So when I check this, I see 12V at the red solenoid terminal (duh, this is connected to the battery pos) and 0V at the black terminal.  But when I push the start button, is that 0V supposed to jump to 12V? 

Because it doesn't.  It stays at 0.  That would suggest there's a break somewhere before the solenoid, right?

thanks 


 

Hey Ivan,
Key on, Ignition on
Grab your meter.
Put it on DC V

put your black probe on the negative battery post(post is the metal part of the battery)
red probe on positive battery post
note voltage

Your starter solenoid should have 4 wires( 2 small 2 big)
Measure the small wires first.

keep your black probe on negative post.
red probe on yellow/red small wire.
note voltage
press start button
note voltage
This is the negative side of your solenoid electromagnet. It is always grounded.
You should have less than .5 V here

move red probe to black small wire
note voltage
press start button
note voltage
This is the positive side of the solenoid electromagnet. When you the press start button it sends +12V down from the start button to the solenoid to activate the magnet in the solenoid. You can hear it click at the solenoid when you press the button.
Voltage here should be 0V. When you press the button you will get close to battery voltage.
If you hold a compass next to the solenoid when you press the button, the compass needle will rotate as the solenoid is an electromagnet. If you have a compass app on your phone, that will work too.

move red probe to one of the large cables on the solenoid
note voltage
press start button
note voltage
I'm not sure of the color coding on these wires. Either this wire goes the the positive battery terminal or it goes to the starter.
voltage-Either it's battery voltage all the time(means it goes to the battery)
or   It goes to the starter and you should only get 12v when you press the starter button. Otherwise it is 0V.

move red probe to the other large wire on the start solenoid
note voltage
press start note voltage
Same as above as I have no idea the color coding of these two big wires.

Thanks F64, extremely helpful instructions.  Did exactly as you suggested.  Key in, ignition on, here are the results:

Battery voltage:11.6 V

Starter solenoid wires, with black probe to battery ground:
Red/yellow small solenoid wire: 0.1 V
Black small solenoid wire: 0V at rest, 2.8V when clutch is in (and the lockout switch engaged), jumps to 10.1V when starter button is pressed
Large solenoid wire (red, leads to battery): 11.6V
Large solenoid wire (black, leads to starter): 0V, no change at all when the starter button is pressed

So...  this would tell me that the solenoid is getting 10.1V when I push the start button.  Not sure why this isn't battery voltage (11.6), but there it is.  However, this is not causing the electromagnet in the solenoid to activate, as evidenced by the fact that there's no voltage coming from the black solenoid wire (the one to the starter) when the start button is pressed.  Right?  So a new solenoid?  I did confirm that the start button has continuity, BTW.

Also, I noticed while I was down there that the fuse box is physically warm to the touch, and there's some evidence of melting plastic in there.  The fuses are OK and voltage at each fuse is what it's supposed to be...  Not sure what to make of that.

thanks again
Ivan


 

You can also bypass the solenoid to confirm it is at fault. Disconnect the starter wire from the solenoid and with jump start cable or a wire with alligator clips, connect it to the positive side of the battery and see if it starts or turns over. Battery and starter are already grounded. 11.6 volts is pretty low, charge the battery and wait a few hours to see if it keeps its charged.

JL

Ivan,
One thing i want you try with the solenoid.
Grab a small length of wire 6 inches.
It doesn't have to be very thick 18 awg should be fine.
Put one end of the wire on the big terminal with the red wire.
Put the other end on the small black wire terminal.
 I want to see if the electromagnet will work with a higher voltage.
10.1 may be too low to pull in the magnet.







Polish,
You are correct about the bypassing of the solenoid, but I wanted to know what was at fault before we replaced parts.
It could have been his start switch, bad ground to the solenoid or corrosion anywhere along those lines.
If he were stuck on the side of the road, jumping the big terminals on the solenoid could get the bike started again.

Ivan,
There is a big voltage drop on the start switch but you may still have enough voltage to pull in the electromagnet.
I'll tell you how to find what is causing that drop.

However, with the fuse block.
Grab your meter.
DC V
key on, ignition on

black probe negative battery post
red probe positive battery post
Note voltage

Move your red probe to the fuse box.
Put it on the terminal on one side of the fuse
note voltage
then move it to the other side of the fuse
note voltage
You should have about a .2V drop from your battery voltage
Any more than that and you have a bad connection between that point and the positive terminal on the battery.
check all of the fuses.
Any corrosion, pinched wires or bad connections will show up as a big voltage drop.
Continuity will not find these problems.
And when checking for voltage drops all connectors must be connected as well as the circuit being on.

Shut off the ignition as the coil will overheat if left on too long.

I'll have to track down the schematic, but finding the voltage drop on the start switch is the same method.
black probe on the negative post.
red probe at solenoid small black wire
Push the start button
You get 10.1V.
move your red probe closer to the start switch along that black wire.
push the start button.
Whenever the voltage jumps up a significant amount from the 10.1V, you will have found an issue.
It will be between that point and the 10.1 measuring point.
There is always a possibility of more than one issue.
You may have to follow that black wire all the way back to the positive terminal on the battery.

Anyway, that's enough for now.
There may be an issue with the starter button as your solenoid small black wire should not have voltage(2.8V) when the clutch is pulled in.
There should only be voltage when the clutch is pulled in AND the start button pressed.
 

Thanks Polish and F64.  F64 you were right about the voltage drop - when I connected battery pos to the solenoid it kicked right over.  I guess 10.1V just wasn't enough.

So I guess I have a break somewhere between the starter button and the solenoid.  I'll take your advice and work my way back along that black wire with the multimeter until I find it.  Any usual suspects or typically bad connections you know of?

thanks guys
Ivan 

The 2.8 V when you pulled in the clutch has me eyeing the start button circuit.
There may be corrosion on that start button as it's passing voltage even though you haven't pressed it.
And when you do press it...it doesn't pass the entire 11.6v.

The screenshot below there are two squares...a pink and a green.
I need you to check the voltage in both those squares.
DC V
key on, ignition on

check battery voltage first

black probe on negative terminal
red probe on each terminal in the green box
2 black wires
note voltage
push start button and check voltages on both wires

move red probe to pink box

black wire
note voltage
push start
note voltage

yellow wire in pink box
note voltage
push start button
note voltage

Hopefully, there is battery voltage at all of those points but my guess it that there is a big voltage drop somewhere.

And i posted the wrong schematic initially... 

 

Thanks F64, you got it!  It was the starter disconnect switch (at the clutch).  It was passing 2-4V even when closed, but this hardly changed when opened.  Basically, it was part open all the time, not passing enough current to activate the starter solenoid.  I just bypassed it and the bike started fine.  Now I'll just decide if I want a replacement for that switch or just to permanently bypass. 

I appreciate your guidance, saved me many hours of dead ends.

Ivan

 

Glad to help out!
Enjoy!