Converting an MKIII Starter to 4 Pole

How educational to read about another famous Norton feature with good evidence of honestly contradicting wear life and replacement practices. How can anything definitive be concluded with such actual variations? The one in a row example that kept track at ~1650 hits per sprag works out to ~412 days if started 4x's a day, give or take moon phase, ambiant temps and luck of supplied parts. Do yoose ES guys ever feel any guilt by not kicking off?

Hobot will let you know the intensity of guilt feelings over-riding urge to kick again and snap leg lesson. I believe that this is an electric assist situation in that you press the little magic button at the same moment as bringing weight down on the kicker so you can have your cake and eat it too. Have never seen an e-start driver actually do that as per driver's manual. :|

hobot said:

How educational to read about another famous Norton feature with good evidence of honestly contradicting wear life and replacement practices. How can anything definitive be concluded with such actual variations? The one in a row example that kept track at ~1650 hits per sprag works out to ~412 days if started 4x's a day, give or take moon phase, ambiant temps and luck of supplied parts. Do yoose ES guys ever feel any guilt by not kicking off?

Click to expand...

I kick start mine. It actually starts easily first kick if I follow the right procedure.

The problem is, it's a 1975 850 Commando MKIII. The side covers say "Electric Start". It came to me without a starter. I thought that it should have a starter since it was supposed to have one. I looked at the options and searched for over a year for an original starter. I found one last week and decided that I should upgrade it to 4 pole since my experience in the 70's was that the 2 pole starter could barely turn the engine over. There are varying opinions on whether the 4 pole upgrade is the right thing to do, and also many swear by Dyno Dave's Hitatci starter which I'm sure is a good option too.

I will likely kick my bike over to start it, because I like the old school methods, although I am starting to get to the point in my life where I may break down and use the electric start when no one is looking just because it is easy.

I plan to go through the engine and will adjust the anti back fire as well as put a new sprag in there. It will all likely last as long as I do, but then again who knows.

Torontonian said:

Thanks from one broken leg Pete to another for these important machining details. This talk has got my mind spinning also as to how effectively to provide lubrication to the sprag clutch area , knowing that oils drip -drain away when needed most , like hitting that starter button cold. So what could provide the lube ? Perhaps a trough to capture and hold oil for that start up critical time ? :|

Click to expand...

So long as you are using a chain primary drive/or belt drive in oil bath Lubrication is provided by the standard components :- the oil scroll ground into the drive gear inner race. This transports oil along the scroll from the alternator rotor/drive gear interface and delivers it to the inside of the engine sprocket. Imagine that the sprag is an open (i.e. no shields) ball bearing. When the engine is running the engine sprocket and sprag revolve together and the individual little sprags need this lube to slide over the drive gear spigot (which is stationary when the engine is running)
Its a bit ironic that at start up, oil is not required at the sprag/drive gear as it can promote slip!

Many years ago I was called to have a look at a Kawasaki Z1300 that wouldn't start, starter motor spinning but not turning the engine over.
After having to make a puller to remove something that revolved on the crankshaft (I can,t remember what it was!) to get to the sprag mechanism I found that the sprag was slipping on its sleeve, a quick degrease and whizz with some fine emerytape to take the shine off and it started first press.

Yikes!

MKIII Prestolite Starter Questions

Ron L said:

Did you just rotate the brush plate 90 degrees or remove and resolder the brushes?

Click to expand...

No, you cannot rotate the brush plate. You remove the brushes from the holder and rotate them to the next brush holder. On some you may need to solder an extension to the brush lead.

I have done a dozen or so of these. I suggest you consider starting with a new reproduction "Prestolite" HD starter and use the Norton armature and drive end cover only.

I typically turn out the drive end cover for a ball bearing and skim the armature fit the bearing. When fitted with larger cables, it makes for a very reliable starter.

Not to say that Dave Comeau's doesn't function somewhat better (newer technology), but for a stock appearance this is the best alternative and I have used one for the last 12-15 years with no issues on a heavily modified 850. The weakest point is the sprag clutch anyway.

Click to expand...

Hey Ron,
I have just rebuilt a 75 Norton and after 30 miles the starter gave up. Wear on the bushes caused the armature to gouge the field coils. what I would like to do is rather than put any more cash into trying to repair I would like to do as you suggested in your post and buy a new Prestolite Harley starter motor type 31458-66A and swop out the cap on the drive end for the Norton original.
1.Is the gear on the drive end the same size as the original ?
2.Is there a part number of the bearing that you fit to the drive side cap ?
3.Is the Harley Starter the same length as the original ?
I know you had stated you have to do some work and you fit a bearing however before I go this route it would be great if you could be more detailed and maybe even post some more pictures . I am in Texas. Thanks in advance.

Ron,
Many thanks for your PM reply. I had two original Norton starter motors. Both armatures were good however the shaft surface on the brush end of one of the armatures had heavy scoring where it had been running in the end cap bearing. On the drive side end cover the bushing was worn on both starters - ditto the brush side end cap. Two of my field coils were also shot in one of the starters. After spending many hours playing around with both I have realised that even though the starter may spin on the workbench if you have any play side to side due to sloppy bushings you are wasting your time. A ball bearing or needle roller bearing conversion is definately worth the hassle. I have now shipped both starters to Ella @ Old Britts (Top notch service and highly recommended)so they can rebuild me one good starter with the original armature + new 4 brush conversion,bearing in drive end cover etc. They have a rebate scheme on your cores so I will report back on how it all turns out costwise $.
Thanks

Sounds like a good option. Fred should be able to clean up the bearing surfaces and build at least one good starter. The important thing is the armatures do not need to be re-wound. That gets expensive.