Starer ring gear teeth

[John]

I've still got the inertia starter motor that came with the car and it as 10 teeth on the pinion.

Out of interest, Lynx sell a pre-engaged starter that enables the bulkhead solenoid to be used, and has a variable mounting plate so the motor can be rotated to different angles.

[wobblyweb]

I have decided what I am going to do...The teeth, although worn, are not bad but as the engine is out and this is the last time I intend to have it out. I will change it for a 110 tooth ring and use my existing starter with 10 teeth. Its been this way for the last 20 years or so, so it should last me out.
Thank you all for your input .
I suppose a summary would be :- it could be 9 or 10 teeth against a 110 tooth ring gear but 9 seems to work best !
Maybe once I am up and running and have stopped throwing money at it I might change to a 9 tooth pinion and report back on the difference it makes.

[Chancer]

Only one can be correct and I suspect that it is the 9 tooth pinion.

Assuming the 10 tooth pinion has the correct module it would require the starter axis to be further outboard to correctly engage, if you have a lathe think of how you have to move the quadrant to accommodate a larger or smaller change Wheel when changing the feed rate or when screw cutting.

Clearly from the postings anecdotally a 10 tooth pinion will work but thats probably due to the large clearances involved and possibly some deflection, it will certainly have too much engagement, will create excessive friction and wear, it will try to turn the engine faster with the same torque output so will be overgeared.

Of course if indeed the 10 tooth pinion is the correct one then the opposite would apply but I think in that scenario a 9 tooth one would not last very long at all.