I recently acquired a B&S opposed twin that needed some starter work, so while I went through the process I decided to do a write-up on it. These starters are such a pain in the rear to work on without any knowledge about them so I hope this might help someone out. In this instance I was switching around the mounting plates from an opposed twin starter to an 8hp single.
I'm not sure about new V-twins and horizontal shaft engines but on older vertical shaft singles and twins there are two main styles.
One that uses a roll-pin to fasten the head:
And the other has a wire clip:
To take apart the roll-pin style the right tool for the job is a blunt roll pin punch. However I have used a nail with the point ground flat or a broken drill bit in a pinch. It's very important to support the head of starter when driving out that pin, otherwise you can break the field magnets. I close my vice jaws down to about a 1/2 inch gap, and lay the head of the starter across that and supporting the rear of the starter with something else. Align your punch, and gently tap out the pin. Some take a little persuasion. Always make sure you punch is somewhat larger than the hole in the roll pin. If it's not, it try to go inside and spread the roll-pin, making it about impossible to remove.
Once that is driven out the head piece just slides off and then you can remove the plastic gear and the drive hub.
The clip style is a bit more tedious. First I lay the starter horizontal on the bench. Then I find a socket about the size of the starter retainer, set it over the top, and give a couple taps with a hammer. This seats the retainer and loosens up the clip a little bit so it's easier to remove.
Then it is just a careful game of prying and pushing that little clip out of the groove. Once it's removed the retainer will slide off, along with the starter gear, spring, and hub. Be careful to remember the order they came apart in. They'll have to go back in that order.
Next I flip the starter over and remove the two long bolts holding the bearing plate and/or the brush plate. Some starters use a separate bearing plate and brush plate and some are combined into one.
One those are removed, you can remove the bearing and brush plates. When you remove the brush plate the brushes will shoot out of their housings. Usually they self contain but keep a close eye to make sure none of the springs get lost.
Here is what is left of the starter.
Now the field magnets/housing and armature are loose and can be removed from the starters mounting plate. (Field magnets on the left, Armature on right)
And the bare starter plate you are left with:
Next post will be on servicing the starter and reassembly.
Now that the starter is completely disassembled you can start swapping parts, refurbishing, or replacing brushes etc.
Before assembling it's a good idea to blow all the rust and corrosion particles out of the armature and the starter itself. I also like to clean the carbon dust off the brush plate, and clean the brush faces with steel wool/really fine sand paper if I'm reusing them. In one of my pics you can see just how much corrosion was in the bottom of that bearing plate. I would wire brush that junk off, spray and blow out the bearing, and put a dab of grease on the bearing surface.
Once the armature is clean, I pay a little attention to the commutator. This is where the brushes ride and make their connection so the cleaner and shinier, the better. Steel wool or really fine (400 grit or better) sandpaper work well to clean it up. Blow it off when it's clean.
If you are reusing the brushes and not buying a new plate, getting the spring-loaded brushes around the commutator can be one of the most frustrating parts of this process. Is use plastic clamps over the top of each brush to hold them in place, then I slide in the armature and start to assemble the starter from the bottom up.
And here is what you will have:
Next is another tricky part; sliding the field magnets over the armature of the brush plate. The magnetism of the magnets can and will try really hard to yank the armature out of the brush plate. I hold the armature and brush plate up against my chest and slide the field magnets over the armature carefully, aligning the cutouts on the field magnets with the brush plate.
Here is what you should have without the bearing plate installed:
Now you just slide mounting bracket over the top of the starter (grease the top bearing surface) and install the bearing cap. Keep in mind the bolts have two grooves in the magnet and can go in two ways. Align the bearing plate and starter mount so the bolts line up, and make sure the starter's power wire is oriented correctly.
Once the bolts are threaded in and tight you can install the bendix assembly. Slide on the drive hub first, then the plastic gear, any washers, and the head retainer. Do not oil or grease the plastic "screw" shaft where the gear sides on. Just make sure it is clean and dry.
The roll pin is easily driven back into place. The clip is a bit of a pain. Here is how I do it. I just be careful to have my fingers grouped closely around the clip so it can't shoot off.
If you've taken the clip off and reinstalled more than a couple times, replacing it is a good idea because it will fatigue.
Note: If replacing the plastic starter gear, it will go on both ways, however the correct way is with the chamfererd teeth UP, facing the flywheel.