Starter won't disengage

[EarlySport]

Hoping someone might have experienced this. I've fitted a lightweight starter to my 911SC ( ebay starter ) and I am almost certain it's not disengaging after starting the car. There is an unusual noise that really sounds like the pinion is staying engaged.

I've bypassed all the factory wiring and fitted an external switch to the solenoid to activate the starter, and ensure power is not getting to the solenoid after starting. This made no difference.

I've filed the mounting holes and large centre boss to loosen the mesh a little - again no difference.

It could be that the noise is from something else and the starter is no problem, but it's a big coincidence that the noise is coming from the starter area and varies with engine revs, and has only become apparent after fitting the new starter.

Does anyone have any clues or next steps? And please don't just bash the ebay starter unless you've used one and had a problem.

Also worth mentioning is this is my third starter in a year. First one (OEM) stuck engaged after starting at a critical moment and I had to continue driving until it failed. Second used OEM starter failed ( solenoid I guess ), and now this lightweight one.

Thanks,

[Gogar]

Have you been able to look at the condition of your ring gear? It's possible that if the ring gear is chewed up, the pinion giear is having trouble coming away.

[john walker's workshop]

flywheel teeth are probably chewed up from the first starter issue, so they hold the starter teeth in mesh.

[MichiganMat]

I bought one from ebay too, a hi-torque starter. The gear is disengaging, just not far enough.

Its squealed and chattered for a little while but its gone away. I don't know what damage if any has been done to either the flywheel or starter, but its quiet now.