Reconditioned Electric Starter Motor: Spinning but Not engaging

[Minijohn]

Hi Iffy650
You said...
I can turn the cog by hand in the direction shown by the arrow  on the end of the solenoid (anti-clockwise when looking on the end of the starter see photo) but by doing that it does not turn the shaft. If i turn it the opposite direction it does turn the shaft.

That sounds like it's working fine because to start the engine the shaft drives the cog, and when the engine is going faster than the starter, the cog freewheels otherwise the engine would drive the starter motor. The cog will never drive the shaft.
Sorry, reading my previous post again it's a bit ambigous. The bendix allows drive in only1 direction, it freewheels in the other.

In your original post you said...
It spins and moves to the correct position but when I held the cog with a big screwdriver the shaft just spins doesnt lock the cog on and drive (the flywheel)
The only thing that takes the drive from the shaft to the cog is the Bendix so that indicates the Bendix is faulty.

Can you post a photo of your bendix in situ - I wonder if it's been assembled incorrectly?

[Iffy650]

Hi,
I was happy with how the starter motor tested on my bench so I put it back in and tried starting. After a couple of times of spinning without engaging it decided to engage and started!
Sometimes it engages sometimes not but it always spins. So, now I reckon it must be an intermittent electrical fault which might be to do with the ignition switch.
Anyone had a similar problem with ignition switch not engaging the flywheel, e.g.solenoid not getting power?

[Minijohn]

You can bypass the ignition switch....

Connect a wire from the positive terminal on the battery.
Touch the other end of that wire to the small terminal on the solenoid.
That will activate the solenoid which in turn will turn the engine over.
(The engine won't start unless the ignition is switched on but should turn over)

If that still gives the same intermittent engagement, I'd check battery terminals, engine earth strap, solenoid connections. Also battery voltage - is the battery any good?

Your original comment bothers me though...
It spins and moves to the correct position but when I held the cog with a big screwdriver the shaft just spins doesnt lock the cog on and drive (the flywheel)
You shouldn't be able to stop the cog turning when the starter is spinning - that would indicate the bendix is slipping.

Good luck