MkIII starter motor - how do I tell if its been converted

If it has Harley Davidson logo on the main body you can be fairly sure its a four brush;0)

The best way is to remove the starter and strip off the brush end cap it's not a big job, undo 3 screws on the primary cover and disconnect the cable, pull the starter from the bike. then remove the two long bolts from the starter motor and ease off the brush cover bearing cap all will be revealed. For best results you want to find 4 brushes as well as four coils in the main body of the starter.

Regards

Katherine

Katherine describes all you need to know to check the starter internals. Some people have converted to four brush but it is pretty ineffective if you only have two field coils. Another conversion is to buy a similar new prestolite starter and use that as the basis for converting to four brush four coil. The advantage of this conversion is that it will look similar to the standard starter but will not be quite as effective as a modern japanese starter as converted. for example. by Norvil. Perhaps even more important than converting or replacing the starter is to make sure that the leads running from the starter and the solenoid are very much more robust (three times the thickness) than the standard wires. With this done and a good strong battery the standard starter can work reasonably well

Tim

Hello Greg

After converting quite a few of the new pattern Harley starters for myself and others and also converting the standard two pole prestolite to four pole, four brush, layout. The one thing that does help the standard prestolite 2 or 4 pole is installing roller bearings.

It really does make the difference, along with upgraded cables and solenoid. so much so i have removed the kickstart on my MK3 as it starts so well and the kickstart got in the way of the rearsets i made!

regards

Peter

Hi Peter,

I have just bought a Harley 4-brush motor to convert the original motor. I was interested in your comments on the bearings. It has always seemed strange that the drive-end of the armature would have a bush; it must generate a fair amount of resistance under load. A ball or roller bearing at that end would clearly be better. What type of bearing did you use at the drive end? Did you build up the housing, as there is not much material there? Did you have to alter the armature land? Do you have any photos of the end result?

Regards, Andy

Previously Andy MacKenzie wrote:

Hi Peter,

I have just bought a Harley 4-brush motor to convert the original motor. I was interested in your comments on the bearings. It has always seemed strange that the drive-end of the armature would have a bush; it must generate a fair amount of resistance under load. A ball or roller bearing at that end would clearly be better. What type of bearing did you use at the drive end? Did you build up the housing, as there is not much material there? Did you have to alter the armature land? Do you have any photos of the end result?

Regards, Andy

Hi Andy,

See:-

http://www.nortonownersclub.org/noc-chat/technical4-commando-forum/370691921?b_start=0#701833263

Tony

Previously Andy MacKenzie wrote:

Hi Peter,

I have just bought a Harley 4-brush motor to convert the original motor. I was interested in your comments on the bearings. It has always seemed strange that the drive-end of the armature would have a bush; it must generate a fair amount of resistance under load. A ball or roller bearing at that end would clearly be better. What type of bearing did you use at the drive end? Did you build up the housing, as there is not much material there? Did you have to alter the armature land? Do you have any photos of the end result?

Regards, Andy

Hello Andy

Here are some photos of modified prestolite end caps

Peter and Tony,

Thanks for the very detailed description of the work done and the photos. I will have to put my conversion on hold whilst I consider options. The starter I bought came from eBay and i had a long chat with Ray, the chap who sells them. He has sold lots of these Harley motors that are basically Prestolite, but unbranded. Having taken it apart, the quality looks good and the internals look very similar to the Norton Norton unit so will accept the armature and end caps. The brush end cap is a straightforward fit with a little trimming of the brush plate to clear one of the Norton cap tangs. Or I could fit a genuine Presolbite four- brush plate that I bought in 1982 for my last Mk3, as this plate is already the correct profile. However, the Norton drive end cap is slightly loose and needs some form of shimming to keep it centralised and avoid armature fouling. Also, a different through bolt orientation, necessitated by the extra coils, means the electrical connection is angled to to the rear - not an issue, just an observation. The donor motor has a needle bearing in the brush end cap but unfortunately the ID is 10.0 mm so no good for the Norton armature. The drive end also has a proper bearing, but I have not separated that from the armature to see what it is, as the the cap is not usable.

Being quite new to this forum, I don't know if this particular motor conversion route has been discussed before - - guess it has?

With your drive bush boss removed for fitting the ball bearing, you must have used a spacer on the armature shaft?

Lots of food for thought now, though there is plenty of time for that, as the frame is with Norman White for major structural repairs, together with several engine/gearbox parts.

Cheers, Andy

Andy

You say several engine parts are with Norman White.

He will most probably try and sell you a PW3 cam. If you want a race cam and the things that go with it fine. Did he ask you what kind of riding you will be doing? most probably not.

If you are wanting a reliable, flexible engine that has plenty of performance to keep up with motorway traffic stick with the standard cam.

the photo is of a WPS starter that has been modified and ready for rebuilding.

Regards

Peter