Starter motor will not start

[Clyde70bmw750/5]

Hi..my 1970 750/5 stopped starting. I took the battery and starter into a autosupply both tested out as good. When I put it all back together and hot wire the selinod tab to the positive on the battery all I can get is a selinod click. This is the same thing that happens when had tried to use the starter button.

Any ideas on why the starter works in a bench test and will not work in the bike.

Thanks...Clyde

[Ken in Oklahoma]

Hi..my 1970 750/5 stopped starting. I took the battery and starter into a autosupply both tested out as good. When I put it all back together and hot wire the selinod tab to the positive on the battery all I can get is a selinod click. This is the same thing that happens when had tried to use the starter button.

Any ideas on why the starter works in a bench test and will not work in the bike.

Thanks...Clyde

Welcome to the forum Clyde.

I'm not sure I'm addressing your question, but here goes.

The solenoid has two jobs to do (as you probably already know). That is to throw the starter gear into mesh with the flywheel and to make the high current connection between the battery and the starter motor.

So when you bench test the starter, does the click include throwing the gear forward?

When you do the bench test, are you directly connecting the battery positive to the heavy terminal? That would be be the heavy terminal that the battery cable was originally connected to. That has to be connected to get anything other than a click.

So the procedure would be to connect the battery positive to that terminal, the battery negative to the body of the starter, and then to jump the battery positive to the small terminal on the solenoid. That should result in the solenoid clicking and throwing the gear forward and the starter motor whirring.

If it is connected as I described and the starter motor doesn't whir that would suggest one of three things. First there are some heavy duty copper contacts inside the solenoid which may not be making proper connection (because they are badly worn or corroded). Secondly you could have a brush problem. Are they making contact and does the armature look OK? The third possibility would be that the armature windings or field windings have gone open circuit. Those can be evaluated by an ohm meter, though you will have to take the starter apart to get to everything.

Editing: Oh, if for some reason you decide to remove the small starter gear from it's shaft--don't! It's an absolute bitch compressing a round heavy circlip enough to get the gear back on. I spent a lot of time trying to do mine on my R75/6 starter, and then only got it after exhausting three different approaches to the job (the last approach risked ruining the starter).


Ken

[Garnet]

Poor battery cables, and or bad ground.

[wirewrkr]

or seized engine.
Does it kick start?

[Ray from Indiana]

did you check your starter relay?

[wirewrkr]

did you check your starter relay?

read his first post. His relay works.

[Major Softie]

Not that I'm arguing with the other possibilities, but it can still be a dead starter. I've had automotive starters before that would spin just fine on the bench under no load, but wouldn't do crap when placed under the load of starting an engine.

[SteveD]

Not that I'm arguing with the other possibilities, but it can still be a dead starter. I've had automotive starters before that would spin just fine on the bench under no load, but wouldn't do crap when placed under the load of starting an engine.

Happened to me this year.

[Roy Gavin]

The battery / starter cable can die under load too - but if you have a set of jumper leads you can eliminate this PDQ