Ford Inertia Starter Motor

Engine Starting Section

This starter motor was used in Ford Flathead, Y-Block, FE, all 6 & 8-cylinder engines
through at least 1964.  The 430 cu in engine had a turned housing and back plate,
because the electrical post was so close to the exhaust manifold, but used all the same
Front (nose) Plate and internal parts.

Click Here to skip to the Starter Drive (Bendix) Gear.


Note: There are four replaceable field windings and four replaceable bronze brushes.

After using penetrating oil, the stove bolt that holds the band on still broke.  I replaced it with a
stainless #10-32 bolt, nut, and lock washer.  Time to take the back plate off.









Notice the red paint inside.  That is General Electric's Glyptol dielectric paint.

Remove all the rust with a wire wheel and notice four rivets on the back are insulated, but four are
bonded to ground.  These secure the brush holders (on the inside).  The insulated rivets are
HOT, with +12-volt potential when running.

Separation isn't easy at first.  It's been bolted together for fifty years.

Just let the brushes fall off the commutator.

I have pulled the brushes out of their holders.  Now the back plate falls off.

New brushes are only about 1/2" long, to decrease resistance.  These brushes look new.


Two brushes are screwed to the housing for a good ground.  These brushes go into the grounded brush
holders.  Also notice NOTHING is soldered.  All connections are crimped or clamped with a screw.



These commutator segments look like brand new.  Beat-up com's look dished, egg-shaped, tapered,
or may be eccentric.  The black cast in the copper segments is actually an embedded coating of carbon,
which is a good-conducting natural lubricant. DO NOT SAND IT OFF!
Notice the old brushes are concaved to match the commutator segments? They are conformed, to pass
hundreds if amps. If you are replacing with new brushes, carefully wrap sandpaper around the com-
mutator with the stones facing up, and carefully sand the new brushes so they conform to the same arc.
Flat-faced brushes can burn your commutator segments. With industrial DC motors, we never change
more than half of the brushes at a time, giving the new ones a chance to naturally wear-in.


Yes, those highly conductive bits of metal need to be washed and blown out.


Notice this brush is bolted right on the case. (Two of them are.)


Here is the outside of the same screw.
Two opposing brushes are insulated (+12 to field windings) and two opposing brushes are grounded.
Current goes into the electrical post and splits. One pair of fields are connected in SERIES, then the
current continues through the insulated brush, through the armature, and out the grounded brush.
The other pair of field windings are connected the same. So, we have a parallel-series configuration. The
opposing same-potential brushes give it away. While half the motor fields are North, the opposing
side is South, so this is a two-pole series wound motor.


Here is a good example of a crimp and solder connection.



I took a wire brush and a disk sander to my housing.








Starter Drive (Bendix) Gear

If the gear is turned out it will lock in the 'flywheel engaged' position.  Centrifugal force unlocks the gear so flywheel speed can return it to the 'jump' position.

Scott from Gig Harbor, WA has shown us other ways to unlock the Bendix gear...

Inside the red box is a steel pin...

Scott uses a steel hook to push the pin back in and spin the drive back up by hand, "You just have to get the initial edge past the pin."

Here is a good picture of the drive gear.  Notice the pin just under the front of the spring.

To remove the pin, pull back the spring then push the pin out. The spring is tough to pull back.
Once the pin is out, the drive gear slides freely off the shaft.

When the spring is pulled back, the pin is exposed.

Now that the pin is out, I simply lift the whole gear straight up to remove.

Here it goes...

Most replacement starter motors come without a drive gear.  They are sold separately, but are still
available at most stores. This one looks real good.

Time to recondition the shaft, end plate, and bearings.





I washed these parts in kerosene, then lightly lubricated using motorcycle chain oil; something that will
penetrate and hang on.












That green/blue stuff on top is moly/lithium grease (from my grease gun in the background).



It's clean, painted, lubed, and bolted together.  The last operation is to insert brushes.  It's easy, if
you use the right tools.  If you don't have them, they're easy to make from a coat hanger.

Here is a brush holder with the spring in the middle.  The brush is hanging out of the window.

Straighten the pigtail, put a hook through the middle of the pigtail and reach down to hook the spring.

Pull the spring up and gently slide the brush into the holder.  Then, let the spring down and remove
your hook.


There it is.  One down and three to go.  At this point, pull the brush by the pigtail.  Slide
it up & down. If the brush binds or the pigtail gets caught, fix the bind before you go to the next brush.

When you are done, the pigtail will not touch surrounding parts and will be free to descend as the
brush wears.  Slide the inspection band back in place, and tighten using a new screw and nut.  Done.

This portion of the gear drive needs to be clean for smooth and consistent operation.