Topic: CB750 solenoid clicking

[Artf0rm]

So I was reworking some wiring today just to make it look nicer on the bike I am building and when I went to start it I heard a loud POP and now the starter solenoid just clicks.  Jesus, what did I do.  Everything else works, front lights, turn signals, brake light.  Just no starter... I even bridged the terminals on the solenoid with a screw driver and still no starter motor.  The battery is good (12.90v reading) So, did I cook my solenoid or do I have greater or lesser problems?

[72500john]

ok tough question to answer. are you getting voltage on the ouput side of your starter soleniod? if so is the volage getting to the starter and does it have a good ground? check this stuff first be fore you get too crazy. you may have grounded out the starter voltage output while fixing up your wiring..but that should have blown the main fuse i think?

[Hush]

Do you have a car jumper cable?
Attach one end to the non battery pillar of the solenoid and the other to the threaded bolt that attaches the main cable to the starter motor, press starter, if this fires up the starter then the solenoid is good but the main cable is fried.
If this does nothing then touch the jumper cable to the other pillar of the solenoid, does the starter now turn over even without the starter button being pressed? Yes=solenoid fault No=something deeper than solenoid/starter problem, look for bad connections/earths.
Remove battery cables and clean underneath them then lightly smear area with dielectric grease and reattach battery cables.

[Artf0rm]

Went back to the garage at lunch today with a clear head and tested the starter with jumpers.  First with positive and negative running straight to the starter.  It turned.  I think tried it with just the positive.  Nothing.  So I connected the large gauge wired normally connected to the solenoid to each other.  On their own this did nothing.  When I put a jumper on the negative terminal and touched it to the starter motor it spun.  I then reinstalled the solenoid and reattached the wires to the terminals.  I touched the negative jumper to the starter motor and turned the key.  The starter motor turned.  I then knew I had a loose ground.  I must have jostled it when cleaning up my wiring.  Another possibility is that yesterday was the first day the bike sat on it's own 2 wheels in a year.  I guess some of the bolts might have shifted a bit and loosened.    Thanks for the sanity check guys.

[Hush]

All good you have wheels again.

[Patrick]

Your starter grounds to the case. You need to pull the starter and clean off its grounds.

Patrick

[Spanner 1]

A bad ground on the frame/engine is your problem and needs to be fixed PDQ to avoid starter current trying to return to the battery on the small frame ground which will also put your rectifier at risk of getting fried ( All this info. comes from a problem posted a few days ago about starter not working  ).
So, remedy is to undo the rear upper engine mount bolt ( with the ground ring terminal under it ) and shine the whole thing up.... take a flat file to the frame bolthole after drawing the bolt all the way out and shine the ring term. good too... good luck. Everyone should do this electrical maintainance to their bike IMO, would solve a lot of starting/ charging/ rectifier problems and is especially important if you have painted the frame.

[Patrick]

I'm having a hard time seeing how a bad harness ground could affect the starter, Spanner. The solenoid has a permanently hot wire running to it and a cable to the starter. The starter is engaged by the starter button, which is a ground on pre-76 750s that completes that circuit. You can jump the solenoid with the key off and the starter will turn, so it is not reliant on anything in the wire harness, except the wire to the starter button.

He might still have a bad ground, but I am having trouble connecting that to the starter.

I just spent two days making a K7 harness work with a K2 right hand switch, so I've looked at that starter circuit a lot lately.

Patrick

[Spanner 1]

I'm talking about the main , fat ground cable directly from the battery - ( Neg. ) pole to the engine/frame grounding point. If that connection is not good as proved in this case ( He can short-out the solenoid 'studs' and the starter still does not turn), only worked when he jumped battery Neg. directly to the engine case.

[Patrick]

Becaue the battery is not grounded, not because of the harness ground. What you are saying I could seem if we were talking about later models. The starter button on 77-78s, at least, is a hot wire. It does need a harness ground to operate. But on his the solenoid reacts when he presses the starter button. That means it is working. When he grounds the starter it works correctly. That tells me the problem is in the starter ground, not the harness.

Patrick

[Spanner 1]

OP... " When I put a jumper on the negative terminal and touched it to the starter motor it spun'...
So, the Neg. connection from the battery to the starter is bad = frame/engine Neg. terminal. Remember the whole bike can work ( unhappily ) away, lights, solenoid 'click' and ignition as the load is very much smaller than the massive amount ( relatively ) of amps needed to crank the starter, which a poor main ground cannot support = no working starter motor 

[Patrick]

If the frame ground is bad I do not see how running a ground wire from the starter to the negative terminal would do ANYTHING.

Whatever.

ArtForm, I suggest you clean the primary frame ground first, since that will be much easier. I hope I am wrong and that's all you have to do. Starters can be a pain in the butt to get out of that cavity.

Patrick

[Spanner 1]

Maybe someone else can explain how your starter works.... looks like your not picking up on my explaination... btw the starter does not ground thru' the starter 'button' like you suggest ... !!.. fried harness would ensue !

[Patrick]

OMG, Spanner. I did not write that the starter button grounds the starter. If you go back to my first post I pointed out that the starter grounds to the case. I said the starter button is a ground that completes the starter circuit and activates the solenoid.

You right. I did not understand your post, only because I DO understand how the starter circuit works and your explanation was based on something you read in another post weeks ago - according to YOUR first port.

Patrick

[Spanner 1]

 Patrick; Reply #7.... ' the starter is engaged by the starter button, which is a ground on pre-'76 750's and that completes the circuit '.......... so the starter 'grounds' thru' the starter button !
What you should have said is the SOLENOID is engaged by the starter button etc... !

In order for the starter to work it must be connectet to the battery ( BOTH + and - ) Great, we know it gets it's + voltage thru' the solenoid, where does it get it's - ??

[Patrick]

The case. The starter grounds to the case. The starter is in no way connected to the negative battery terminal of a pre-75 750.

[Spanner 1]

Oh !.. right, I see......