MK III electric starter replacement

Hello all.

I am finally about to repair my MK III electric start system. A couple of years ago the sprag broke and engaged the starter while the motor was running; and destroyed the starter. I have been using the kickstarter (always a 1 or 2 kick, starter), but my knees are getting old. I have an old Boyer.... so I'm looking at replacing:
Electronic ignition
Starter
Sprag (and maybe engine sprocket and starter gear).

Trying to decide between:
Pazon Altair or Tri Spark
Dyno Dave starter or CNW chromed 4 brush conversion

The race on the engine sprocket has some minor indents from the sprag. Can they be cleaned up or will it be out of tolerance?

Totally unrelated...but did the MKIII battery side side cover come with a tool compartment? My first Commando (when I was 18) was a 73 Interstate and it had one. My current MKIII does not...and I wish it did.

Any comments, advice or suggestions would be most appreciated.

nberg said:

Totally unrelated...but did the MKIII battery side side cover come with a tool compartment? My first Commando (when I was 18) was a 73 Interstate and it had one. My current MKIII does not...and I wish it did.

Click to expand...

There's no space behind the side cover due to the Mk III battery, however, the Mk III models did have an under-seat tool tray.

"15...06-5616...Tooltray, Under Seat, MK3"
http://www.oldbritts.com/nor_mk3_75_35.html

I'm using the Pazon Altair and DynoDave starter. Works well for me, but then again I've no experience with anything else except the original system.

Sorry, can't address the sprag, I switched out starters because the commutator on my OEM starter failed.

re starter motor, if you're a purist then neither will do.
Functionally they are both vastly superior to the Prestolite.
Add a heavy set of cables too.
re the freewheel assembly, dimples on either of the wheels is problematic but may not be a bin job altogether.
When any of the sprag elements are in the dimple the remaining elements are carrying the load.
The instance of that happening is only when the 14 element sprag is replaced by the 18 element cage assembly or vice versa.
You can be sure that if the number of sprag elements is the same as the one that made the dimples that they will cog together again at some point.
I would wager that 99% of MK111's that have ever kicked back at start up will have dimples and will go on to function adequately.
IMO the three items, chainwheel-sprag-gear are more or less maintenance items if you have an engine that kicks back routinely.
As far as grinding either of the running surfaces is concerned and staying within the tolerance that the spag calls for? probably not. Look up the sprag manufactures numbers and then measure your used parts. Likely you will be out of tolerance before you do any grinding at all.
A new gear and chainwheel are not inexpensive, but it makes a proper job of it.
The used ones you have will need to be tried with the new sprag cage assembly to see if they are acceptable to you if they are not replaced.
The biggest concern is what you already experienced. The lock up and subsequent destruction of at least part of the starter gear train.
You wouldn't expect anything much different again if you don't fix the whole problem would you? You could ruin a new starter motor just as easily as the previous one.
I am looking for some old ones to experiment on if you are going to bin them for new ones. I'm sure we can easily come to terms.
re the EI, all you care about is taking care in avoiding kickback regardless of who makes what. Early Boyer and a low battery is a known culprit.
All the best whichever direction you head in.

I remember reading a post on the NOC about sleeving these items. I think I remember they were purposely rough turned and a sleeve was loc-tite'd in place IIRC.
Nose around a bit over there and see if you can find it.
All the Best.

I have a friend who converted his mk3 from a standard starter to a Dyno Dave starter, and he said that it was probably the only aftermarket part that he has fitted that was worth its money.
I also use a Dyno Dave starter and it spins the engine over effortlessly, but I can't compare it to a standard starter as I never had an original starter. How it compares to a CNW 4 brush, again I wouldn't know.

I have fitted a Trispark ignition unit, and the first one failed after about 2 years causing me to have the Norton recovered, and after getting the bike home the bike would run for short periods normally before temporarily failing, even though it apparently didn't show a fault when tested by Steve Kelly on the bench, but the second Trispark unit that I have fitted (which I was asked to make a contribution to due to the original being out of warranty) has so far behaved faultlessly. I have no experience with a Pazon as previuosly I had a Boyer mk3.

nberg wrote;

Can they be cleaned up or will it be out of tolerance?

Click to expand...

I believe that the tolerances for the gear/sprocket to be as follows.
Shoulder on internal gear 1.625"-1.626"
Internal gear diameter on sprocket, 2.282"-2.281"