Mon Dec 19, 2022 1:32 pm by cornbinder89
I am one if not the 1st one, to recommend running the battery direct to the starter/engine and then grounding the frame and body from there.
It is hard to check a starter with an Ohm meter because the resistance of the coils are all less than 1 ohm.
You can check the armature/commutator for shorts to ground, each bar must be infinite Ohms between the bars and the armature shaft.
There are mica separators between the bars on the armature. They must not come up to the surface the brushes ride on. As the commutator wears, the copper bars wear and/or are turned on a lathe to true up. Once that is done, the mica is "under cut" with a thin blade to about 1/8"-1/16" below the level of the bars.
The correct way to check a armature is on a devise called a growler. If you don't have that, it is hard to check out an armature.
The field coils can be checked be checked for continuity and for shorts to ground. power enters at a contact or stud, on the inside of the motor, it splits into two paths, each path go though a det of two field coils (four field coils in all) a north and south coil on each leg. The brushes are in the "outlet" of the field coils. In other words the armature and brushes are in series with each leg of the field.
When you take the brush band off the motor, you can separate the field coils from the brushes The brush wires are screwed to the end of the field coil. Once the brushes are separated, the through bolts can be removed and the rear cover with the brushes can slide off the commutator. WHen that happens they will snap in (springloaded) and you will have to hold them out to re install.
WHen the brushes and rear cover are off you can look over the brushes and brush holder. The "hot" brush holders are insulated from the motor case. The earth brush holders are grounded to the case.
When the through bolts are removed, the starter will come apart in to is component parts. The rear cover, with the brushes and rear bearing and thrust washer, the main case with the field coils and pole shoes, the nose cone and front shaft bushing and the armature, which will come out toward the front or drive end, it will not come out the brush end. (edit: should say the main case will come off the brush end, not the armature. You can't install the armature in the brushes and slip the main case down over it. Don't know why my mind muddled that up).
The three external pieces go together in only one orientation, there are locating pins in the mating faces The through bolts must not come in contact with the field windings or the wires from the brushes.
There are thrust washers on both ends of the commutator shaft, At leat one on each end are a close fit to the shaft while others are a looser fit. Take note of what order and placement on the shaft when you disassemble and put them back in the same order.
This is a lot to try and explain in words. over the .net. If what you want to know is: Is the starter motor good? The easy way is to hook to a battery and make sure it spins when energized. If it does that, don't disassemble but lube the front bushing with light machine oil, and fill the oil cup at the rear. If there is a lot of play in the nose cone, remove the through bolts and slide the nose cone off, but leave the main body and the rear cover together, and replace the nose bushing.
The rear of the armature rides directly cast iron rear cover. For this reason the oil cup and oil wick inside is the only source of lube for the shaft. If it is dry it will drag, and wear the shaft and housing. In my view neglecting to keep it full of oil is the source of much of the problems.
WHen doing the spin test, the motor should kick hard when power is applied, if it doesn't almost kicj out of your hand, then there are problems. There are many internal problems that can happen, but it is hard to walk you through all the test.
That being said. The same armatures were used in a lot of starters and is available NOS or aftermarket. The Aftermarket are cheap enough, that if your armature needs work just buy a $45 replacement armature and change it.
Last edited by
cornbinder89 on Fri Dec 30, 2022 10:53 am, edited 1 time in total.