Help needed starter motor will not disengage 

On the bench the starter works as it should.  In the car it keeps turning with the key removed.  

The 12v is only on when the key is in the start position.

If I remove the main 12v direct to the battery the starter motor sops and when the wire is put back on it dose not turn the engine “normal until I try and start again then starter mot dose not disengage 

Perhaps a relay in your electrical system between key and starter solenoid that is sticking.

 

 

The starter motor works on the bench perfectly.  If I take the solenoid wire off it still runs on.

also it’s a brand new starter motor that I have used before the engine rebuild?

I have just taken the engine out and removed the clutch and flywheel and reinstalled and it’s the same.

Try lube to the pull in linkage, WD40?

You will probably need to remove the motor to do this.

Of corse there is allways percussive maintenance, hit it with a big hammer

 

It sounds like your putting the main battery wire on the solenoid term NOT on the main starter term  

 

I have an issue with the solenoid.  Once engaged I have 8v back feeding from the main battery terminal.

So that I understand correctly.

Starter was good before rebuild and nearly new.

In the car ignition switch to start and starter turns engine over.

Release ignition switch and starter keeps going.

Pull wire off starter solonoid and it keeps going? This is the part that is interesting.

Yes to all.

so with the starter motor running on I took off the wire to the solenoid and still running on.  Put my volt meter on the solenoid terminal and had 8v. 

For the solenoid to pull in or hold in it requires current to flow.

With the solonoid wire disconnected current should stop flowing.

The fact that you see 8V at the terminal makes me think that there is a connection in the solonoid to the high current motor contacts. 2 things come to mind either some swarf has got in or there is distortion within the solonoid (it is bent) causing a short

The company I bought the starter motor from are sending me a replacement Solenoid.

Just a thought have you took the main earth strap off the engine when you removed the starter 

New starter motor arrived today bolted it on and worked as it should do.