You would think that one woudnt mesh properly, there has to be a ratio of ring gear to starter pinion of an whole number ' i think 10 to 1 otherwise it will eventually wear out. however maybe the 'mesh' between the two is intentionally loose enough to not matter for the time the engines cranking.
when I took my starter for recondition he gave me one with 10 mine was with 9 he said it wouldn't matter, but when we came to fit it we found the holes for the bolts didn't quite line up! so I took ti back and he change the face and back to 9 teeth
Certainly the Mini starter doesn't 'quite' fit on the bolt pitches - but easily sorted with a round file! The starter itself fits snugly into the backplate ok. Yes - I assume 10 would crank faster - but only if sufficient amps. So - what is the original Minor fitment - 9 or 10 teeth ? From above - looks like 9 ??
The starter I replaced (broken bendix) was 10 tooth. The replacement from ESM was 10 tooth, and one I got from Livingston Autoparts as a spare is 9 tooth. Apparently they both work, but the nine tooth has slightly different winding turns so spin speed is the same as 10 tooth. All very confusing (for me anyway)
well I've broken 3 Minors in my life for spares and a mini the starters I got are all 9 tooth except 1! which is 10 tooth one the Minors I broke were pick-ups and the van I'm restoring has a 9tooth starter maybe LCV had a 9 tooth? maybe the Low compression engines?