Article and pictures by Alex Varv
This article is well overdue. For some reason it slipped from the "to do list" for many years. Since I received an old M21Y Cors-Air engine to be repaired I decided, among other things to take pictures and explain how to clean, repair and overhaul an electric starter. The engine belongs to Josh Welliver currently residing in California. Thank you Josh for allowing me to publish "portraits" of your electric starter.
To make this easier for the reader to understand the whole procedure, we will number each phase:
1) Remove the two front bolts that hold the starter on the starter plate; remove the clamp with rubber insert from around the starter if present. If this safety feature is not present,
look into ordering the safety bracket, clamp, rubber insert, washers, bolt and nut. If not supported, the starter may beak off in flight!!!
Before opening the starter clean it with gasoline or carburetor cleaner!
Before opening the starter, please make a note of the position of the notch in the starter housing with respect to the positive terminal. This notch MUST be to the right of the positive terminal of the starter as seen in the picture below. This will insure that the magnet polarity is correct. Incorrect polarity will cause the starter to deliver LESS torque thus the engine may be difficult to start.
2) Using a Phillips screwdriver, remove all the screws that hold the starter together and make sure you do not lose any parts. Spray generously all the parts with carburetor cleaner and for stubborn spots, use a small brush as well. Make sure you do not lose the two springs that put pressure on the brushes!!
Using a scoring pad (3M ) or very fine sandpaper wrap it around the commutators and with gentle pressure turn the rotor in both directions. This will remove the dents, craters, scratches and carbon deposits from the commutators, allowing a better contact commutator/brush thus giving more power!!
3) Now we will concentrate on the brushes and the brush holder. Remember that the brushes are pushed against the communtators with springs. Do not lose them.
After checking again for deposits and ensuring that the brushes , the brush holders and the springs are clean and that the brushes slide freely in their holders, use a soft wire and as shown in the picture below, keep the brushes deep in the holders. This will allow to reinstall the rotor. Try to immobilize (hold the brushes with the wire) as low as possible so at least the upper 1/3 rd of the brush is above the wire.
4) The next step is to install the rotor. However, in some cases, the brushes will still be too far out to let the rotor slide down. In this situation,
using a small screwdriver, gently push each brush in the brush holder. It is sufficient to slide the rotor down far enough to keep the brushes in position.
If the brushes are not fully retracted, they will NOT let the rotor go down. In this case, use a small screwdriver to push the brushed further
into the brush holders until the rotor passes the upper part of the brush.
In the picture below, we can see that the rotor commutators passed the brushes so that the brushes are in place.
Now you can remove the wires and push the rotor as far down as it will go.
5) With the rotor installed in the gear holder with the brushes, we can now install the starter housing with the magnets. Please be aware that the bottom of the cover (housing) has a bearing. The rotor shaft will have to be guided in such a way that the shaft will enter the center hole of the bearing. This can be easily achieved when we press the rotor down by slightly moving it from side to side. Make sure you do NOT remove the rotor from the gear housing that contains the brush holders.
On worn starters, it may happen that when pushing the rotor into the gear box housing, the bearing is pushes out (as shown in the picture below)
If this occurs, degrease the outer rim of the bearing and apply Locktite and press the bearing in place.
It is very important that a certain position of the starter cover with respect to the gear housing (with the brushes on it) be kept.
If we do not keep the orientation as shown below, the magnets polarity will be off thus the starter will have less torque!!!
6) Having the rotor installed and the starter cover with the magnets correctly set, make sure that this position is kept, so that before inserting the screws for the final assemblage of the starter, the orientation of the notch is as shown in the picture above. Now we can proceed to install the bendix.
Using a syringe or an oiler, apply oil to the clutch, bendix shaft and spring.
7) The next step is to install the bendix in the gear box holder and to install the bendix cover (housing)
First we must lubricate the gears. For this I use bearing grease mixed with Lithium grease
Apply the mixed grease to the bendix gear and to the rotor gear as well
The bendix has two washers on each end (shaft) They must be installed before the bendix is inserted the gearbox or the bendix cover is installed over the bendix
Now we can proceed with installing the bendix housing (cover)
As shown above make sure the positive terminal is centered in the bendix housing so the black round insulator can be pushed in.
This concludes the electric starter overhaul.
We provide some replacement parts as brushes, gaskets and the whole bendix.
NOTICE: This article will be a good reference to other types of electric starters , not only the ones used on our Cors-Air Engines
Finally, we strongly recommend that a SEPARATE ground is provided directly from the negative of the battery to the starter.
On many occasions and on MANY paramotors that I had the pleasure to see in my long PPG career, I noticed that some machines do NOT have a separate ground.
Some may say that the engine body is the ground and because the electric starter is mounted to the engine there is a ground. Very true.
However, from my experience I noticed that in many cases this ground is NOT enough because there is resistance in it. Providing a separate ground, will increase the starter RPM thus ensuring an easy engine start.