Inspecting the starter….

After seeing that the starter decided to no longer work on Saturday I removed it, the carburetor, and the battery. I brought all three home since the starter and carb need some love, and the battery could use a charge. I decided to check the starter first because I could have a perfect carb and full battery but neither would do me any good if I can’t turn the engine over. First order of business is to take the bendix off of the starter. The bendix is what engages the engine to make it turn with the starter motor and then release the starter from the motor once the engine is running.

In the pic above the motor is the big thing toward the bottom, the bendix is upper left, and the starter switch is upper right. With the bendix off I turned the motor shaft by hand to see if there was any binding. The motor has a little bit of drag to it, but it wasn’t sticking at any position in the rotation. Looking in the cut outs on the right side of the motor  I could see the brushes and commutator were packed full of carbon. That needs to get cleaned up since it gums up the motor and can cause a loss of power as electricity can jump to areas it shouldn’t be. Time to take the motor apart.

I was kinda surprised that the long screws that hold the whole thing together weren’t frozen in place. The would be the two screws center top in the pic. The end plates are upper left, armature lower left. If you click on the picture to make it larger you can see the end plate with the brush holder is caked in carbon, and a trail of carbon chunks leading from the motor housing up to where I set the brush holder down. What a mess, carbon sticks to everything and you can’t just wipe it off. If you try then you just smear it all over whatever your trying to clean up with.

A closer look at the commutator end. All that black carbon in between the commutator segments can cause your motor to run weaker. It can allow some of the energy that should go to the winding you are trying to energize to go to other windings. This means the winding you want to energize isn’t as strong and other windings can energize weakly, but enough to further impede your starter. All of that needs a good cleaning and a piece of pegwood to dig the carbon out between the segments.

Mmmm. More carbon dust. The field coils look good though. A quick check with a meter shows that they don’t have any breaks in the wire and aren’t shorted to the case. I don’t like to remove field coils that have been in place for a long time.  I’ve found that the insulation can become brittle over the years and sometimes it creates problems that would never have happened if they were just left alone. Now to the brushes.

Well that’s ugly. Every one of them is worn at an angle. Someone didn’t take the time to make sure the springs that hold them in place and press them against the commutator were centered. The concern here is that the brushes won’t be sitting straight in the holder that they are supposed to slide in. By sitting at an angle they can bind in the holder and stop making contact, and then the starter won’t turn. To make sure they didn’t bind I cleaned up the brush holder plate and then tested the brush holders themselves for shorts to ground. The ‘hot’ brush insulators are still good and the ‘ground’ brush holders weren’t insulated, exactly as it should be. once cleaned up and inspected, I put the motor back together and made sure the brushes didn’t hang in their holders. I also tested the brush springs for proper tension and found them satisfactory.  Next step is to take the battery and a good set of jumper cables and see if it spins…..

I’ll let you know once I’ve done that.