Bike tries to engage when I connect the battery

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kevenc

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Hello fellow XS650 enjoyers!

The electrical wiring on my bike is a nightmare (looks like a spaghetti).


Since I bought it, I've been having an intermittent problem, both front and rear right turn signal would stay on even when my ignition switch is "OFF". That problem did go away for a certain time, also as you already know of my last thread, I've been having trouble just starting the bike, the last time I tried jumpstarting it, as soon as I connected the jumper cable the bike when trying to start without my pushing the electric start button. So I figured I'd switch the battery with a new one, and same thing happened, as soon as I connected the black pole it tried to start on it's own again. What could be the most common cause of this?


1714421103110.png
 
Sounds like either the starter relay has its contacts stuck closed. Or there's 12 volts energising the starter relay which should only be there when you press the start button.

Best to check out the starter relay first to see if it permanently closed by welded contacts for example.

If it checks out, then you need to find what's sending 12 volts to the starter relay that shouldn't be. HTH
 
I'm a literal beginner, I know that on the bike there's a Motogadget m-unit control module, I thought that took care of everything electrical on it. Is it possible that with that ECM, there's no starter relay on the bike ? I'll have to remove the tank to have a better look.
 
Its been a long time said:
Sounds like either the starter relay has its contacts stuck closed. Or there's 12 volts energising the starter relay which should only be there when you press the start button.
Click to expand...
I absolutely agree, either the starter relay has stuck contacts or something is making the contacts close as soon as power is applied.
And yes, your starter definitely needs a hefty relay, even though you have a M-Unit.

For starters (pun sure as heck intended :D ), please tell us the year of manufacture for your MC. The wiring changes almost year to year and details matter.

Now for some simple step-by-step troubleshooting instructions:
1. Find the starter relay first. It isn't hard. It is the biggest relay on the bike and has a big thick cable running to it from the battery. The relay will have another thick cable running to the starter. Disregard that for now.
2. Find the two thinner wires on the relay and disconnect them (there are likely to be some bullet connectors on them).
3. Connect the battery. Does the motor crank? If so, the relay is bad. If not, the wiring is bad.

Let us know what you find!
 
Thank you both for the reply!

Lou_TX said:
I absolutely agree, either the starter relay has stuck contacts or something is making the contacts close as soon as power is applied.
And yes, your starter definitely needs a hefty relay, even though you have a M-Unit.

For starters (pun sure as heck intended :D ), please tell us the year of manufacture for your MC. The wiring changes almost year to year and details matter.

Now for some simple step-by-step troubleshooting instructions:
1. Find the starter relay first. It isn't hard. It is the biggest relay on the bike and has a big thick cable running to it from the battery. The relay will have another thick cable running to the starter. Disregard that for now.
2. Find the two thinner wires on the relay and disconnect them (there are likely to be some bullet connectors on them).
3. Connect the battery. Does the motor crank? If so, the relay is bad. If not, the wiring is bad.

Let us know what you find!
Click to expand...

XS650 1974. I'll update as soon as I can, quick question though. If the contacts are stuck or welded, will I need a replacement starter relay?
 
The only way power can get to the starter is through the solenoid, and the only way power can get to the solenoid is through the starter button. So, your starter button is either stuck or cactus...
 
No idea your problem lies. Answers given make sense where to start.

If you gonna learn to trouble shoot a loom here is a good place to start.

https://www.xs650.com/threads/continuity-testing-made-easy.49917/

Now i don't know anything about M-units. This diagram was posted on here by a member who did their own wiring. might help but the wire colours may differ

M Unit 01 (2) reize 3500 Copyright.jpg
 
What’s the actual benefit of the m-unit - looking at it on the schematic - it appears just to be a connection between all the different switches, or is it a large fuse box ? To me it seems like just adding to the electrical system that’s already there! Something I don’t get ?
 
Niels B said:
What’s the actual benefit of the m-unit - looking at it on the schematic - it appears just to be a connection between all the different switches, or is it a large fuse box ? To me it seems like just adding to the electrical system that’s already there! Something I don’t get ?
Click to expand...
I won't even pretend to understand all the unit's functions but just looking at the page for the upgraded unit (now the "mo-unit"), my memory didn't even scratch the surface. So instead of explaining it, here's the page itself:
https://motogadget.us/products/mo-unit-blue
 
UPDATE!

Alright so I installed a new starter relay, and the problem still persists. I managed to re-wire a couple thing and it seems like my electric circuit is fine.

I've done some testing with a Voltmeter and spotted the problem. Even with my Ignition Switch at "OFF", no light on the M-Module, there's still 12V going out from the "START OUT" to the solenoid. I'm thinking the M-Module might be kaput, any idea ? But at the same time, it works fine for everything else.

For now, I unplugged the solenoid positive wire, so I can kickstart my bike and ride without it trying to engage on it's own, but I'd like my electric starter to work.

I'm at lost
 
Last edited:
Try disconnecting the wire coming out of the M-unit to the solenoid. That stop the starter? If it does, it points to the M-unit being at fault.
Is there a "reset" procedure for the M-unit? I'd try resetting it and see what that does.
Have you emailed the M-units folk? Could be it's a common thing and they have a ready answer.

All this assumes of course that you wired the M-unit correctly.
 
1714785247845.png


I have this model, i'm not sure if there's a reset procedure. I've seen online the one for the new model, tried it and didn't work. Contacted Motogagdget waiting on their answer.
 
Last edited:
If the M unit is sending 12v to the starter relay even when it's in the off state then I agree as said above, it has to be faulty? Is there another output on the M unit with high enough rating to try as a check? Are any other M unit outputs passing 12v when the M unit is in the off state or just the starter relay output?
 
Here's a wiring diagram for a bike, in PDF format. Apparently it simplifies the electrics by making it more complex, uses fewer cables, makes it easier to add accessories and gives you something to do on weekends - completely rewire your bike.
 

Attachments

  • Universal_m-UNIT_Blue_Diagram_5.0.pdf
    2.7 MB · Views: 13
For the non adventurous: I converted the image to jpeg, but this site wouldn't accept it for some reason, so, I uploaded it to media then copied and pasted it. What a load of rubbish all that just to post a bloody picture.
Click to expand...
 

Attachments

  • 1714811324556.png
    1714811324556.png
    679.3 KB · Views: 26
kevenc said:
Could it be that something is plugged in reverse and giving it's power directly from the solenoid ? Considering that when the IGNTION LOCK is OFF, there's still 12v on the START O from the module while the rest give 0v ?
Click to expand...
If your starter solenoid has one side hardwired to ground and the other side is constantly energized with 12V from the M-unit, something definitely seems wrong, I agree.
I assume there's a way to configure the unit. Any chance you can connect to it and view the current configuration?
Again, knowing pretty much nothing about the unit, I'd still expect some kind of a configuration where it says which output pin/wire is controlled by what input pin/wire and via what logic (direct, inverted, and, or etc).
 

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