Starter Motor swap

The story - for some reason, my car treats starters as consumable. I seem to have trouble with one roughly every 3 years. This time, the starter that was on it reached 4 and a bit years so it was overdue.

The trouble started with occasional failure to engage properly and ended with a complete failure to do anything. This is similar to what happened a few years ago on a trip to Madrid & Bordeaux. It got to Madrid OK, but starting got progressively worse and worse, and we were lucky to be able to get home. I was fully expecting to have to bump start it to get off the ferry, but it held on until we were home and then died completely. I've had a few exchange units and refurbs over the years.

Anyway, having decided that I really don't want another M80R in there as they seem horribly unreliable for me (combination of Lucas & Magneti Marelli), I went for a LotusBits WOSP special.

WOSP logo
Shades of Eddie Jordan?
LMS 042-LB

Note the suffix

Label on the motor body showing the LMS 042-LB model number
The whole starter motor

The suffix in those photos matters. Others have tried this style of starter and found that it doesn't engage properly with the ring gear. The problem is that the pinion throw isn't always right. Lotusbits have done a deal with WOSP to get a "perfect" throw, hence the LB suffix.

So - to work. First, disconnect the battery lead in the boot. If you don't do that, you're going to get fireworks later.

Then remove the air filter housing, filter and air box (8 nuts holding the trumpets to the carbs + a couple of pipes and a throttle return spring). You should see something like the image below.

The old starter motor in place.

Undo the M8 nut that holds the positive leads from battery, alternator etc. to the motor (13mm socket) and unplug the solenoid exciter wire. Tuck the cables carefully out of the way. This is also a good time to check the connection to your oil pressure sender (the "can" sticking out of the block above the motor).

Motor power connections and mounting bolts

Now, to remove the motor.

M10 x 80mm is the spec. for the M80R, a 3M100 will have M10x65mm. Whichever you have, a 17mm spanner on the bellhousing side is essential.

You'll have to do it by feel unless your eyes are on stalks.

Withdraw the motor and put it to one side.

Photo of different mounting bolts. Old M80R are longer.
M10x65mm (3M100 mounting) vs. M10x80mm (M80R mounting)
Side by side photo of old and new motor
M80R vs WOSP
Photo showing deeper mounting flange on the M80R vs. the shallower WOSP mounting flange.
Why size matters

You can see why the M80R needs longer mounting bolts. Replace them with M10x65mm if necessary.

Fitting the new motor is "the reverse of removal" as they say.

And finally, motor in place. The cables need a little bit of rerouting so it's worth getting them onto the post and holding them in place with the nut finger tight on the stud until the motor bolts are fully tightened. Don't forget to put the rubber boot onto the cable before clamping it onto the motor. The extra insulation will be useful if you're working in that area in the future.

Clearance is a little awkward for the top mounting bolt but it can be done with a long socket and wobble bar.

Final steps - make sure the nut on the stud is tight, reconnect the battery and make sure the new motor works, then refit the airbox, filter and cover.