M201 starter motor

A dodgy or dead starter motor may not mean the need for a replacement unit which is a pretty expensive item. If it spins but does not engage it may simply need cleaning. If it has become intermittent or has stopped working completely it could simply be time for some new brushes. Before describing how the brushes can be replaced a bit of information of some of the other faults that I have encountered.

SYMPTOM POSSIBLE CAUSE WORTH INVESTIGATING
Starter sometimes behaves as though the battery is almost flat, struggling to turn at any speed. At other times it works fine. Assuming that all connections (batteries, isolator, earth, and starter motor) have been checked and are clean and tight it is worth checking if the the battery isolator in more detail. It is a sealed unit but is easy to bypass by connecting both cables to just one of the terminals. If the problem disappears then the fault lies in a poor contact being made within the isolator. (I've had this on one of my jeeps).
Starter turns okay but does not always engage with the ring gear to turn the engine. This is probably the most common problem I have come across. The most likely cause is a build up of sticky mess in the helical splines of the bendix and / or on the shaft that the gear has to move forward along to engage with the ring gear on the flywheel. it is possible to get rid of most of the muck (a combination of grease , oil and clutch dust) without stripping the motor down. Click here for more details.
Starter has become intermittent or simply does not turn at all. Again, assuming that all connections in the circuit are clean and tight, it is possible that the brushes have worn down to the extent that they no longer make good contact with the commutator.

 

 

Brushes worn down this far will no longer work. This starter motor became intermittent turning slowly sometimes then springing to life at normal speed. It was as though there was a poor connection but checking the cables didn't solve the problem as the poor connection was between the brushes and commutator,

  

This second example (above) shows a part worn brush still able to make good contact with the commutator. It is a later type of brush though where only one brush in the set has insulated sleeving. Where this is the case the brush with no sleeve must be connected to the end plate as shown rather than to the field coils.
 

Having dismantled the starter motor and made a note of where everything goes check and clean the copper commutator to remove the carbon deposits on the surface and between the segments. There is hardly any wear on the example shown but as long as the commutator isn't too badly worn fitting a new set of brushes is still a worthwhile exercise.

  The original braded cable from the brush is soldered into a lug. It is difficult to remove the old cable from the lug as I think it was both crimped and soldered. It is easier to cut off the old cable and solder the new one beside it as shown above. You will need a good soldering iron for this rather than a miniature one for electronics.
 
The cable from the second old brush (connected to the field coils) is cut off leaving a short stub. I do this as the field coils are aluminium and it is difficult to solder to aluminium without special solder and flux.   Both the stub and the end of the brush cable need to be tinned with solder then a solder joint made between them. Take care not to damage the insulation that prevents contact with the casing.
 
Before reassembling the unit it is worth cleaning the helical splines by pulling the armature away from the front plate. Dust from the clutch plate tends to build up on the grease. If it gets to bad the starter will not always reliably engage into the flywheel. This example needed cleaning and lightly greasing.   Reassembly is best performed with the motor supported in a vice in a vertical position as shown. The end shaft and the two washers on it have been cleaned and lightly greased and the insulated sleeves put back onto the securing rods ready for the casing to be lowered back into place.
 
With the casing in place the brush connected to the field coils is fitted into its retainer on the end plate ready for the plate to be replaced. This is the fiddly bit but with patience and a couple of small screw drivers it can be done.   The problem is that the brushes have to be held back against the tensioning springs to allow them over the commutator as the end plate is lowered onto the shaft. A extra pair of hands are useful but with patience it can be done alone.
 
The thrust washer can now be refitted. Note that the plastic washer sits between this and the spring. All moving surfaces are well greased before assembly including the surface of the end plate. It is necessary to hold the shaft at the front carefully with some grips whilst tightening the nut.   Finally the end cap can be replaced and the securing nuts tightened. Before reconnecting the field coil cable to the solenoid check that the surfaces that make contact are clean and free of corrosion. Before returning the starter motor to the jeep clean the front shaft where the bendix gear moves forward and lightly grease.

I can supply new brushes in sets at the following cost:

UK - 1 set of brushes inc packing & 1st class post = £5.50

Europe - 1 set of brushes inc packing & sent by airmail = 6.00 Euro

Worldwide - 1 set of brushes inc packing and sent by airmail = £7.00

The brushes are made to Ducellier specification by a reputable UK manufacturer but have to be ordered in large quantities which is why I am able to offer these for sale.

Please note the brushes are for the Ducellier 24 volt starter motor fitted to the Hotchkiss M201 they will not fit 6 volt WW2 starters on MBs and GPWs ! If you would like to order a set of brushes please e-mail me.