The Big Starter Motor Mix Up Disaster ! (Part 1)

posted in: GTT Blog & News

BEWARE! VERY IMPORTANT – Useful for Gen 1 Mini owners but the principle is the same across all models

End of starter motor broken off/cracked? Aluminium swarf in the clutch bell housing? Damaged ring gear? Starter Motor Destroyed Your Flywheel?

Here is why!

Many auto-factors, eBay sellers and even real OEM are either wrongly listing and or wrongly supplying starter motors and sometimes customers are assuming they’re all the same and purchase. There are at least 3 different starter motors on the generation 1 mini that will physically bolt on to the W11 engine block.
They may share some or most internal parts and physically bolt to the block. However the nose on some are the wrong size & shape, this is why people are seeing the end of the starter motor casing broken off or ground to dust (aluminium swarf inside the clutch bell housing). The other main important issue is that the starter motor gear having the wrong size, pitch and tooth shape will destroy the flywheels ring gear… it appears to just roll over the top and mash up the teeth!
We strongly recommend anyone buying a starter motor to order it directly from BMW with your Vin and reg. (Even a BMW main dealer could get it wrong) measure twice fit once.
Note: cars may have some information changed including numbers and or engine swapped (or transmission including auto to manual conversion)! 
Some units may have the correct nose shape and size and yet the WRONG gear size, pitch and tooth shape! (due to how some pattern parts are just “thrown” together with incorrect parts by unknowing assemblers) as seen with other pattern items (including driveshafts)
From research and feedback it is now clear that many people have had this issue with either stock and aftermarket FWs
Quotes from people answered:
“it was very tight bolting up” – This is because the nose is the wrong shape and size. It would have been fouling on the flywheels ring gear and the bolts tightened before it was fully seated. 
“the starter motor came loose” this is most likely because it was never fully seated as described above. once the nose had broken/fallen off the body would lose tension against the block.
“it made a clunk/bang when first starting but seemed ok after” – don’t wait to find out what could happen, remove it and inspect. (probably cracked the starter motor)
“It sounds strange when starting sometimes”This is where the wrongly matching starter gear is “mashing” your flywheel on the ring gear, it will just roll over the top in places where the pitches do not match. You may get your car to start up for a while until there is not enough contact left!
“can’t be the starter motor that damaged the FW, they either work or they don’t “These are not pre-engaged starter motors!, these are an inertia system, the gear is “thrown” outboard  to engage with the FW ring gear… this type is known to get stuck engaged with the FW ring gear when the starter motors get old…. this is where wear and damage occurs (there is no lube on either gear, so they wear!).
“this is the 2nd/3rd starter motor and or flywheel I have replaced due to damage/failure in a small amount of time” You are still fitting the wrong starter motor or a previous one has damaged the ring gear to a point where it won’t crank… even with the correct starter motor now installed it’s too late….. luckily some aftermarket flywheels including GTT have replaceable ring gears, perfect for scenarios where the starter motor destroys them!
NOTE: The Gen 1 R53/R52 Cooper S  S, JCW & GP1 MANUAL  GEARBOX (all years) all have the same identical FW from factory There is only 1 OEM BMW FLYWHEEL for the  It is Made by LUK. (listed as the original OEM BMW PART)
(Part numbers can change)
See How our GTT Ring gear 100% matches the OEM FW ring gear on the same model (R53/R52 Cooper S, JCW, GP! Manual)

See how another brand alloy flywheels teeth for the same model does not match (yes it is damaged but still the wrong formation)

Close enough, is NOT good enough!

Follow our guide for buying a new & correct starter motor.

1) Try to only purchase from BMW MAIN DEALER/BOSCHE. ( item will probably be on exchange, you will pay the main dealer a surcharge.) This will be refunded by dealer later ( as long as the old SM is serviceable. ) Also it allows you to compare the new unit to your old unit BEFORE fitting.
2) You must quote your Vin Number AND REG.
4) Measure everything!

However even a BMW dealership can supply the wrong part… be careful to carryout checks and measurements before installing…. also if you have an incorrect starter motor already, make sure you are not ensuring the new one matched that! ASSUME NOTHING.

Having spoken to BMW, their listings don’t give an option for R53 Cooper S auto or manual. Also states that the R50 Cooper AUTO is the same as the R53 Cooper S (we don’t know if this is true) and that the R50 cooper is different again. All we can recommend is precisely comparing your new item to the original factory fitted starter motor from your car ONLY.

See Part 2 Here