M-Unit Wiring (Starter)

[Cadergray]

Hello everyone!
My 83 cs 650 is my first bike build and when I received the bike (for free) it hadn’t run for years. After a couple days we got it running but the wiring was shotty. I am doing a cafe racer build and decided to replace my loom with an m-unit blue. I have started wiring the unit in finally but I am terrible at wiring and when I wired my starter in for testing the frame ground wire was smoking. I am using 6 gauge wire from the battery to the solenoid with a 40 amp fuse. The solenoid clicks on when I hit the start button but the starter doesn’t turn and the wires get hot. Also no warning lights flash on the M-Unit. Any ideas on what I could be doing wrong? Thank you

 

[jpdevol]

Unhook positive terminal from battery post. Just as a precaution, I'd first unhook the 6ga from the starter motor itself and tape it up to keep from potential arcing until you get the issue sorted.

Can you roll-over the engine via kickstarter or rotor nut?


It's unusual, but the starter itself could be locked/frozen or even shorted inside. The gear-train between starter and crank could be bound-up or mis-assembled.

Those issues will require right side-case removal. I'd verify those issues before going back to electrical diagnosis.

Any pics or diagrams of wiring will be helpful. I am familiar with the M-Unit.

 

[Adamc]

Unhook positive terminal from battery post. Just as a precaution, I'd first unhook the 6ga from the starter motor itself and tape it up to keep from potential arcing until you get the issue sorted.

Can you roll-over the engine via kickstarter or rotor nut?

Is there continuity between the starter motor terminal stud and engine block?

It's unusual, but the starter itself could be locked/frozen or even shorted inside. The gear-train between starter and crank could be bound-up or mis-assembled.

Those issues will require right side-case removal. I'd verify those issues before going back to electrical diagnosis.

Any pics or diagrams of wiring will be helpful. I am familiar with the M-Unit.

I agree with JP above. It sound like something is stuck.
Im also a novice auto-electrician and installing an an M-Unit. Im hoping to start the Ignition side today.
Have you bench tested the M-Unit with a mock up loom to see its actually working?
The power up phase of the m-unit has to complete to self check its systems (All lights fast pulse for a while from a cold / initial power up).
It a simple process with a battery / Common grounds, plus a lamp wired to test the circuits and a switch of some sort.
Try You tube for help (Classic Octane / Cognito / Revival Etc...).

 

[Cadergray]

Unhook positive terminal from battery post. Just as a precaution, I'd first unhook the 6ga from the starter motor itself and tape it up to keep from potential arcing until you get the issue sorted.

Can you roll-over the engine via kickstarter or rotor nut?

Is there continuity between the starter motor terminal stud and engine block?

It's unusual, but the starter itself could be locked/frozen or even shorted inside. The gear-train between starter and crank could be bound-up or mis-assembled.

Those issues will require right side-case removal. I'd verify those issues before going back to electrical diagnosis.

Any pics or diagrams of wiring will be helpful. I am familiar with the M-Unit.

Unhook positive terminal from battery post. Just as a precaution, I'd first unhook the 6ga from the starter motor itself and tape it up to keep from potential arcing until you get the issue sorted.

Can you roll-over the engine via kickstarter or rotor nut?

Is there continuity between the starter motor terminal stud and engine block?

It's unusual, but the starter itself could be locked/frozen or even shorted inside. The gear-train between starter and crank could be bound-up or mis-assembled.

Those issues will require right side-case removal. I'd verify those issues before going back to electrical diagnosis.

Any pics or diagrams of wiring will be helpful. I am familiar with the M-Unit.

Hey JP thanks for the advice! I can get you some pictures of the temporary harness once I get back from Air National Guard drill. So first I can kick the bike over, I have disassembled the clutch adjustment screw because it has gone bad and I need to source a replacement. Also I don’t believe the starter is bound since we used the starter to originally start the bike. Although it has sat for some time so I may need to double check the gear train like you mentioned.

 

[Cadergray]

I agree with JP above. It sound like something is stuck.
Im also a novice auto-electrician and installing an an M-Unit. Im hoping to start the Ignition side today.
Have you bench tested the M-Unit with a mock up loom to see its actually working?
The power up phase of the m-unit has to complete to self check its systems (All lights fast pulse for a while from a cold / initial power up).
It a simple process with a battery / Common grounds, plus a lamp wired to test the circuits and a switch of some sort.
Try You tube for help (Classic Octane / Cognito / Revival Etc...).

Hey Adam! Sounds like we can do our M-Units together! I did setup a bench test and paired the M-Unit with my phone.

 

[jpdevol]

The starter draws a lot of current (35 - 75A) so the wires from the solenoid will get warm. Obviously the "frame ground smoking" is bad.
What size wire is the frame ground?

 

[Cadergray]

The starter draws a lot of current (35 - 75A) so the wires from the solenoid will get warm. Obviously the "frame ground smoking" is bad.
What size wire is the frame ground?

Right that’s why I had the 6 ga going from the battery to the solenoid but my frame ground is also 6 ga

 

[jpdevol]

OK. Obviously serious issue somewhere. Post back when your service is completed and when time allows. A sketch of wiring layout is helpful too in addition to pics. Might be prepared to remove and examine starter & its guts - depends on what wiring shows.

 

[miketweedie]

Double check that the frame ground is on bare metal on both ends. When I test-ran mine it also got smokin' hot and it turned out the ground strap was not getting clean contact. I added a temporary second ground strap from one of the case bolts to the negative terminal and problem solved, so I knew the existing ground was insufficient.

Whenever I swap wiring I always beef up the ground wires, file contact points to bare metal and add a smidge of dielectric grease. It doesn't take very much paint/rust/oxidation to significantly reduce continuity.

 

[Cadergray]

Double check that the frame ground is on bare metal on both ends. When I test-ran mine it also got smokin' hot and it turned out the ground strap was not getting clean contact. I added a temporary second ground strap from one of the case bolts to the negative terminal and problem solved, so I knew the existing ground was insufficient.

Whenever I swap wiring I always beef up the ground wires, file contact points to bare metal and add a smidge of dielectric grease. It doesn't take very much paint/rust/oxidation to significantly reduce continuity.

Awesome will do, I was guessing something wasn’t getting grounded correctly. Next time I work on the bike I will try these new solutions. Also my bike never came with a key, any ideas on how to get the gas cap open?

 

[jetmechmarty]

https://www.xs650.com/threads/lost-my-gas-cap-key-anybody-have-a-spare.52224/

Post #5 by @5twins

 

[Cadergray]

https://www.xs650.com/threads/lost-my-gas-cap-key-anybody-have-a-spare.52224/

Post #5 by @5twins

Thank you very much

 

[Cadergray]

So is there a way to get the old cap off without the key? I’m going to replace the cap and I don’t need the original ignition key because I am putting a new one in. I don’t have a local locksmith because I live in the boonies.

 

[jetmechmarty]

So is there a way to get the old cap off without the key? I’m going to replace the cap and I don’t need the original ignition key because I am putting a new one in. I don’t have a local locksmith because I live in the boonies.

In the red circle, see the tab. Push it back toward the lock. Use a can opener or small screwdriver, or....

 

[JesseeS]

And if a picture don’t work, here’s a video courtesy of @Jim

 

[Cadergray]

And if a picture don’t work, here’s a video courtesy of @Jim

Thank you Jessie and Jet I appreciate the help, any keyless cap recommendations?

 

[Cadergray]

OK. Obviously serious issue somewhere. Post back when your service is completed and when time allows. A sketch of wiring layout is helpful too in addition to pics. Might be prepared to remove and examine starter & its guts - depends on what wiring shows.

Alright J I have returned from drill, I pulled the starter this morning and it was very rusty and I had to extract the bolts this ruining them. The barrel of the starter and the copper pads are very worn and have surface rust. I think it would be in my best interest to get a new or used starter, but I can’t find any on eBay. Any suggestions?

 

[jpdevol]

Maybe pics to help evaluate - rather rehab than replace if possible

How did the ground check-out per Mike above?

 

[Cadergray]

Maybe pics to help evaluate - rather rehab than replace if possible

How did the ground check-out per Mike above?

Ground was good this time but the solenoid would click and the starter would jolt but not crank the motor over

 

[jpdevol]

Here ya go -