Starter solenoid/battery wiring

herpdderpder

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Hi all! I'm starting on this project bike and found some issued already (bad starter solenoid). Additionally the bike was already worked on and some things were disconnected so I don't have a good point of reference. I'd like to make sure I get this part right when the new part comes in: What connects to the starter solenoid?

I looked at the wiring diagrams and here's what I see:
Positive from battery to solenoid​
Starter switch from the solenoid to the switch (yellow/red and green/purple)​
Starter motor positive to the other terminal on the solenoid. (blue/red?...)​
Ignition positive to battery? or to the same pole as the battery to solenoid?...does it matter?​

Looks like blue/red should have a another wire with a connector that terminates it to the solenoid...right?
20240707_222621.jpg
 
I give up, what bike are you working on?
On the CM400/450s, blue/red goes between the fusebox and the electric start switch. Red/green is part of the electric start safety interlock circuit, connected to the starter solenoid and grounded by either the neutral light switch or the clutch switch. The yellow/red wire is connected to the solenoid, fed 12 volts from the handle bar switch, to crank the electric start.
 
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I'm not familiar with your bike at all, but here's the specific wiring diagram in case it's more model-specific than what you have.

However, please put your bike model in your signature or remember to mention it in posts so we won't have to go through your profile to find out what you're working on. Thanks

1720445321900.png
 
That Red/Blue goes to the Oil Pressure switch - standard color for all Hondas around that era from what I've seen. So you'll need to locate that switch, there should be a wire attached to the back that matches this plug. Looks like this, but with a very small ring connector and red/blue wire bolted to the stud on the back:
1720449007346.png

4 connections go into the switch, the red/yellow and red/green - these go to the start switch (red/yellow) red green runs through the starter interlock circuit (bike must be in neutral or clutch pulled in to start)

So the four connections to the left of your thumb are all correct, assuming your hand is screening the connection from the two heavily shrouded wires to one pole of the switch.

The empty pole in the photo would then be from the starter to the solenoid.
 
Load could be the left or the right, I've seen them both ways. It should have this little boot on top, which gives you a good indication of which way it should be wired. Either the fat red wire or the starter cable will have a ring terminal with a 90 degree bend at the end. That side goes through the "upright" part of the boot, with the other through the "sideways" part. The tab with the slot goes over the little bump out created by the Green/Red and Yellow/Red and the little hanging part has an end with a small tang that holds just on the lip to the left of your pinky (you can kind of see the clean spot). Since you're going through all this, now is the time to wire it correctly and get the boot on there in the proper orientation - otherwise it'll never sit right.

1720455835170.png
 
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EzPete said:
That Red/Blue goes to the Oil Pressure switch - standard color for all Hondas around that era from what I've seen. So you'll need to locate that switch, there should be a wire attached to the back that matches this plug. Looks like this, but with a very small ring connector and red/blue wire bolted to the stud on the back:
View attachment 34442

4 connections go into the switch, the red/yellow and red/green - these go to the start switch (red/yellow) red green runs through the starter interlock circuit (bike must be in neutral or clutch pulled in to start)

So the four connections to the left of your thumb are all correct, assuming your hand is screening the connection from the two heavily shrouded wires to one pole of the switch.

The empty pole in the photo would then be from the starter to the solenoid.
Click to expand...
Thanks! I was trying to trace out the positive connection from the starter motor and thought it was the blue/red (which had to be wrong because that wire is tiny)
 
I just noticed in your original post that you're replacing the solenoid - have you confirmed that it is indeed a bad solenoid, and not something with the interlock/safety circuit?

This can be tested with a multimeter. you're looking for a closed circuit at the red/green pin with either the clutch level pulled in, or the bike in neutral. Ideally both will independently close the circuit, but it'll work with an either/or while you chase down the issue with the other switch.

Obviously, the starter switch circuit as well should be tested to make sure it's closing as well with the button depressed.
 
The Blue w/Red connector by the solenoid is unused. On the SC models the oil pressure sender is on the oil cooler and the wire runs down the front frame tube from the instruments.
If you look at the wiring diagram by the Neutral/Overdrive switch you'll see a "rectifier". If that is missing the starter circuit is dead. The part is found at the left side cover, it's a small Black box with 2 wires.
In this picture it's to the left of my finger, this is a CM electrical panel. Similar but no the same.
GEDC2548.JPG
 
You can actually bypass that whole setup to test just the starter switch function (or if there's bad neutral switch) by tying together the two leads from the clutch lever switch.
 
mike in idaho said:
That's a diode, it's mis-labeled as a "rectifier" on several of Honda's wiring diagrams. Two terminals, it will pass current one way but not the other.
Click to expand...
1720466221568.png

Just a joke ^^^^
Don't get mad at me. I'm just trying to help the OP identify the components in the starting circuit, and in the diagram it says "rectifier"
 
Yeah - on the CX's it's marked the same and I spent a bunch of time looking for a rectifier to find it's an in-line diode buried in the fuse compartment.
 
esmith250624 said:
Just a joke ^^^^
Don't get mad at me. I'm just trying to help the OP identify the components in the starting circuit, and in the diagram it says "rectifier"
Click to expand...
You'd have thought their translation issues would have been better in the '80s
 
That diode/rectifier thing was bugging me trying to figure out what it was there for on schematic. It is inline with the neutral switch being used as a return path to ground for the starter coil. Separates it from the alternative clutch switch as return ground on starter coil. I suppose so your neutral indicator light does not go on when activating the clutch switch. With that diode pulled you can start it with with clutch switch activated, but not just in neutral.

Sometimes they use a diode to shunt a relay or coil flyback voltage, and it might actually do this in neutral, but I don't think that is it's function. There's nothing a little flyback voltage will hurt in these old bikes. My thought is always pull the clutch in when starting to avoid putting all the starter coil amperage thru the neutral switch which is buried in the engine and would be tougher to replace than the clutch switch.
20240707_105157.jpg

These schematics freak me out, I get lost in all the lines. I wish they could be broken up into more functional units.
When I had this apart I was thinking the Yellow and more green coil wires were bolted together, but schematic seems to show the yellow as 12v from starter switch and the greener one the return path. So I assume they are separate connections, but they look like they go to a singular post. I didn't take them apart, but probably should have to clean up and examine.

It also would have been neat to measure how much current is drawn from this relay to activate it. I'd guess it's some thing like 500ma to 1A. That's enough to erode switches, as you probably know from issues with that starter switch on the handle bars. It get's flaky. Add to it the cut-off for the headlamp during start, that's like 4A with a older incandescent bulb.
 
They do actually tie together on the later CBs and CXs (I think the CM’s as well but not certain)

The diode is there to allow for an either/or with the neutral switch or clutch lever to allow the starter switch to pull the magnet closed that jumps the terminals for the starter.

It’s likely just a safety device to avoid starting in gear, as you can totally bypass the entire circuit and the starter functions fine.
 
A closer look on my CM450 and CM400 shows they are two separate wires. I also measured the coil amperage draw with a multimeter(on 10A range), it showed 2.5A draw. Connected between connection at clutch switch and ground, with starter disconnected at the relay coil.
20240709_170505.jpg

My neutral switches are different, here's the CM450, it's got two wires:
20240709_171758.jpg

Here is my CM400, with one wire:
20240709_173536.jpg

And they do look like they would come out and replace easy enough.
 
It would appear from the schematic that extra wire on the neutral switch is the OD(6th gear) indicator on the CM450. A indicator on tach labeled 'OD' lights. So it is a different switch, two in one.
 
kbongos said:
It would appear from the schematic that extra wire on the neutral switch is the OD(6th gear) indicator on the CM450. A indicator on tach labeled 'OD' lights. So it is a different switch, two in one.
Click to expand...
Correct, the 450 has the Neutral wire and 6th gear(O/D) wire, since the 400 in most cases is a 5 speed there's only the Neutral.
The switches are not interchangeable! Different internal lengths which will lock the shift drum, don't ask how I know :ROFLMAO:
 
I will mention that two pin canon plug with the red wires and fibreglass sleeving show obvious green corrosion on them. You should trim that back until the wire is no longer green and re-crimp with new connectors. Follow it to the left side where the reg/rec is and fix there as well. This is common on these bikes that had an old battery sit in them for many years. Otherwise you may burn up that wire and lose all electronics, blow fuses, and causing a higher rate of charging because it's trying to push more voltage to compensate for the high resistance in the wire.
 
ancientdad said:
I'm not familiar with your bike at all, but here's the specific wiring diagram in case it's more model-specific than what you have.

However, please put your bike model in your signature or remember to mention it in posts so we won't have to go through your profile to find out what you're working on. Thanks

View attachment 34441
Click to expand...
whoever made this color diagram is a SAINT
 
Sorry to resurrect this older thread, but does it matter which post on the solenoid takes the hot/red/positive cable? If so, and the solenoid has no + or neg indicatiors, which post gets which cable?
 
The small wire energizes a coil that makes a plunger make contact between the two posts, so it doesn't matter which cable goes to which post.
 
Doesn’t matter. They’re both the same side of the circuit. Positive battery terminal to the starter. Switch closes the loop.
 
Well, it does matter if you still have the covercap (shown above in posts #6 and #17) and want to continue to use it installed correctly...
 
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