Converting an MKIII Starter to 4 Pole

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Well, Jim's stock MKIII certainly starts quite well (and looks great). I have to agree the stock charging system is totally inadequate and 3 phase is the way to go.

On it's best day my stock starter would crank about the same and had it not been kicked back upon by the Boyer I might still have it. Had I known that a 3 phase conversion was so easy 20+ years ago I would have done it then. Perhaps if the kickback mechanism wasn't seized tight the sprague would have survived. I have the stronger sprague in it now along with a three phase and DD. It spins way faster and the heavier sprague seems ok with it. The kickback mechanism is now working and adjusted properly but with the Pazon I don't thing it will ever see any action.

I wonder if being in the mountains give the starter a little easier chore? My compression chart shows to expect about 85% of the sea-level pressure at 5000'.
 
comnoz said:
I am vary familiar with the anti -backfire device. They seldom need adjustment unless you have installed a larger starter motor or you are attempting to overcome an over-advanced ignition.

The video should work now. Jim
Click to expand...

Yes the video worked. Your bike started much easier than mine ever did. The original MKIII I had in the 70's would start the first time if it was warm out then it would growl at me after that. That was when it was brand new. I think there was a reason that they called it a "Starter Assist".

It likely was the crappy batteries we had back then.

As with any identified problem we may be over doing the mod but is that really a bad thing? I ask this because the issue might not be that a more powerful starter puts more strain on the system as much as the sprag being damaged by back firing from timing or a low battery and an ignition that does not prevent back firing.

Can the starter really put too much force on the sprag if the system is properly adjusted?
 
come on jim you need to listen to most on here and get rid of the choke's on those amal's. after all they are more trouble than there worth and not needed. :lol:

comnoz said:
I am vary familiar with the anti -backfire device. They seldom need adjustment unless you have installed a larger starter motor or you are attempting to overcome an over-advanced ignition.

The video should work now. Jim
Click to expand...
 
JimNH said:
Well, Jim's stock MKIII certainly starts quite well (and looks great). I have to agree the stock charging system is totally inadequate and 3 phase is the way to go.

On it's best day my stock starter would crank about the same and had it not been kicked back upon by the Boyer I might still have it. Had I known that a 3 phase conversion was so easy 20+ years ago I would have done it then. Perhaps if the kickback mechanism wasn't seized tight the sprague would have survived. I have the stronger sprague in it now along with a three phase and DD. It spins way faster and the heavier sprague seems ok with it. The kickback mechanism is now working and adjusted properly but with the Pazon I don't thing it will ever see any action.

I wonder if being in the mountains give the starter a little easier chore? My compression chart shows to expect about 85% of the sea-level pressure at 5000'.
Click to expand...

Yes, Pueblo is at 84% and that helps. But the bike has been at many rallys at sea level also and has never had a problem since the charging system and battery were upgraded.

Before that it was just a kickstarter assist and the headlight was pitiful -even at 84% air pressure.

There is no question -eventually the sprag is going to fail. It does not get enough lubrication to keep it from wearing flats on the bottom of the vanes. But I still have to think that a hard hitting starter is going to reduce the life even more.

So regardless of whether you want to do a starter upgrade or not -I would suggest spending money on the charging system/battery before I would spend money on a bigger starter. My experience has been that it isn't really needed. Jim
 
Hello again
As requested by Torontonian the machining details for the drive gear sleeve mod
This mod increases the angle of the sprags so it has no chance of 'flipping' and consequently wrecking the sprag/drive gear/sprocket
Obtain a LRT354220 hardened bearing inner race from your local bearing stockist (should cost only a few pounds, I got two for less than a tenner)
Turn/grind the drive gear spigot (what engages with the sprag) down to 1.450" diameter. make sure you have a good radius tween the spigot and gear i.e. NO UNDER CUT You can do this with the needle roller still in place, just plug the bore
turn/grind the bore of the your new inner race so it has an interference fit of 0.002" (1.448") chamfer the bore so it will sit over the radius
Press the two together ,remount in the lathe and turn to length.
Turn/grind the OD down to 1.632" (this is an increase of 0.007" over standard)
radius the end so it is an easy fit in the sprag.
Job Done
Ken Merrick did his mod a little differently, he glued the sleeve to the drive gear with loctite retainer. He also internally ground out the engine sprocket to remove the sprag dig in marks (approx 0.010") and increased the size of the sleeve accordingly. I have found that it is not necessary to do this.
Even if you have to pay someone to do the machining for you it should work out cheaper than replacing crunched bits for new ones.
The drive gear and bearing sleeve can be turned with sharp carbide tools but I used a toolpost grinder to finish the diameters (Same toolpost grinder i used to reface the cam followers)
My last commando (thirty years ago) crunched its sprag in Stockholm (Sweden) when I was going to the Britti Ralli in Finland. Thank goodness for kickstarts! That bike had a two pole starter. This was years before I got myself a well equipped machine/workshop.
Belt drives run dry and this starter system do not mix well. The sprag requires lubrication or it will prematurely fail, If it fails and seizes the sprocket to the drive gear you will kiss your motor goodbye as the starter motor will not be able to withstand the huge increase in revs (60,000 plus) If you do have to run a belt drive make sure it can run in an oil bath (with oil!)
I run a duplex chain on my Mk3 primary drive as according to Andy (the chainman) No one makes decent triplex chain anymore.
Regards
Pete
 
dobba99 said:
Hello again
As requested by Torontonian the machining details for the drive gear sleeve mod
This mod increases the angle of the sprags so it has no chance of 'flipping' and consequently wrecking the sprag/drive gear/sprocket
Obtain a LRT354220 hardened bearing inner race from your local bearing stockist (should cost only a few pounds, I got two for less than a tenner)
Turn/grind the drive gear spigot (what engages with the sprag) down to 1.450" diameter. make sure you have a good radius tween the spigot and gear i.e. NO UNDER CUT You can do this with the needle roller still in place, just plug the bore
turn/grind the bore of the your new inner race so it has an interference fit of 0.002" (1.448") chamfer the bore so it will sit over the radius
Press the two together ,remount in the lathe and turn to length.
Turn/grind the OD down to 1.632" (this is an increase of 0.007" over standard)
radius the end so it is an easy fit in the sprag.
Job Done
Ken Merrick did his mod a little differently, he glued the sleeve to the drive gear with loctite retainer. He also internally ground out the engine sprocket to remove the sprag dig in marks (approx 0.010") and increased the size of the sleeve accordingly. I have found that it is not necessary to do this.
Even if you have to pay someone to do the machining for you it should work out cheaper than replacing crunched bits for new ones.
The drive gear and bearing sleeve can be turned with sharp carbide tools but I used a toolpost grinder to finish the diameters (Same toolpost grinder i used to reface the cam followers)
My last commando (thirty years ago) crunched its sprag in Stockholm (Sweden) when I was going to the Britti Ralli in Finland. Thank goodness for kickstarts! That bike had a two pole starter. This was years before I got myself a well equipped machine/workshop.
Belt drives run dry and this starter system do not mix well. The sprag requires lubrication or it will prematurely fail, If it fails and seizes the sprocket to the drive gear you will kiss your motor goodbye as the starter motor will not be able to withstand the huge increase in revs (60,000 plus) If you do have to run a belt drive make sure it can run in an oil bath (with oil!)
I run a duplex chain on my Mk3 primary drive as according to Andy (the chainman) No one makes decent triplex chain anymore.
Regards
Pete
Click to expand...

I will have to keep this in mind.
Jim
 
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 ? :|
 
When working properly, is the standard rm 23 180 watt alternator not capable of keeping the battery fully charged?

My MK3 battery generally shows 12.8 to 13.2 volts after a short ride, stock RM23.


Glen
 
I don't want to spend MORE cash on bigger alternator output also ...Always run lower watt halogen pilot light daytime anyways. Hesitant to go Lithium due to fires on Jumbo aircraft and even the new Lithium cellphones. :!:
 
worntorn said:
When working properly, is the standard rm 23 180 watt alternator not capable of keeping the battery fully charged?

My MK3 battery generally shows 12.8 to 13.2 volts after a short ride, stock RM23.


Glen
Click to expand...

The standard MK3 alternator may just be capable of providing enough charge to make the starter dependable with highway riding and a reduced wattage headlight.

If you throw in a halogen and some lower speed running then it is hopeless.
The biggest improvement with the 3 phase alternator is that it provides enough current to charge the battery and run the headlight at 3500 rpm whereas the single phase alternator puts out its stuff way up there at 5000 rpm.

The voltage you are seeing after a ride is just surface charge. It really means very little as far as the actual state of charge.
Check the voltage again after 24 hours and then you can compare the voltage with a charge percentage chart for the type of battery you are using. Jim
 
I have seen the following numbers quoted in a couple of places, not sure if they are correct. If they are, 75% at 2400 seems ample, at least compared with my 60 watt Millers etc on the other old bikes, all of which get the job done (sort of).
75% at 2400 is 135 watts, plenty for a 60 watt headlight and Boyer.
I have also seen the figure 140 watts at 3,000 rpm quoted for the rm 23.
Either number seems a good surplus over the load, if these figures are correct.

Couldn't get the post in without being clipped. The claim is that the single phase rm 23 and the three phase rm 24 both produce 180 watts @5000 rpm but the three phase produces 85% of peak power at 2400 while the rm 23 gives 75% of peak at 2400 rpm.
This seems like a lot of power?

Converting an MKIII Starter to 4 Pole
 
I would be surprised if any of them actually kept up with their specs at least after using them for enough miles for the rotor to have lost it's edge. [not long]
I do know the stock MK3 alternator will not provide dependable starting with average use. Jim

ps, A stock alternator might do ok with a led headlight. I will not consider riding a motorcycle- day or night without a headlight on. jim
 
Another bit of food for thought re the two pole/four pole discussion and the idea that a soft engagement of the sprag (2 pole) might reduce wear.
The modern Triumph 955i uses a starter sprag. On the early T595 versions, when the sprag fails, it often is cheaper to find a complete replacement 955 engine than pay shop time for the repair!
On the later bikes the sprag can be changed quite easily.
Apparently the sprag on all of their engines is very durable if the battery voltage is kept high. In my operators manual, Triumph warns that starter sprag problems including possible breakage will arise with low battery voltage causing weak or soft engagement. Triumph found that it is better for the sprag to engage fast and hard rather than gently.
This might be one argument in favour of a four pole over a two pole on the Norton?
It might also explain partof the multitude of prematurely broken or worn sprags on Commandos, especially if the stock charging system and battery are on the weak side.

Glen
 
worntorn said:
Another bit of food for thought re the two pole/four pole discussion and the idea that a soft engagement of the sprag (2 pole) might reduce wear.
The modern Triumph 955i uses a starter sprag. On the early T595 versions, when the sprag fails, it often is cheaper to find a complete replacement 955 engine than pay shop time for the repair!
On the later bikes the sprag can be changed quite easily.
Apparently the sprag on all of their engines is very durable if the battery voltage is kept high. In my operators manual, Triumph warns that starter sprag problems including possible breakage will arise with low battery voltage causing weak or soft engagement. Triumph found that it is better for the sprag to engage fast and hard rather than gently.
This might be one argument in favour of a four pole over a two pole on the Norton?
It might also explain partof the multitude of prematurely broken or worn sprags on Commandos, especially if the stock charging system and battery are on the weak side.

Glen
Click to expand...

My take was the sprag was damaged by a low battery because it turned the motor slowly causing it to nearly stop on compression and then jump ahead after compression making the drive chatter. Listen to one with a weak battery. jim
 
Also in many cases toss in worn AAU stuck in advance and electronic ones over advancing backfifres from low voltage brain scramble. Rita more low volt tolerant but don't know what they do on low voltage. Too bad Norton didn't put money in compression releases to ease muscle or electric starts. Was there ever a service release note on vendors to stock up and owner to keep two around? Its better for past decades automactic transmissions life to be set to up shift sharply under decent throttle than set soft smooth or let off torque durring shifts. I was rather pleased at the pay back of having chain saws cryo tempered as stopped having to adjust tension or sharpen by 3-4 x's > so someone with a history of sprung sprags might try it and see if worth while there. Maybe a special coating would ease the engagement. Otherwise seems innately unsolvable.
 
Since Dyno Dave has sold hundreds of his starters maybe he can provide some feedback on sprag life.

My gut feeling is that a solid engagement is preferable to tepid engagement but I have no data to back that up.

I am convinced that the stock alternator is useless unless all of your riding is headlight - off, something I won't do, or all high RPM. Now in my 60s, I like back roads, some of which have heavy enforcement through small towns. Between that and the summer tourist traffic often I'm at low RPM where the three phase is still working. I also like the voltage monitor light in place of the stock indicator as it gives useful information.
 
Dynodave startor starles me with the instant violence of torque and made me wonder if the engagement system could stand it but maybe its helps it. Commandos are not for the un-thinking owner but a huge battery helps lower pilots attention and no big deal for just curising around. Could always help it with KS unless/until some reason ya can't, I'd fudge ign time for easy safer starts rather than best power. If ya stay in lower gears much to keep in charge zone might consider ATF in AMC box to extend sleeve bushes and clutch basket wobble.
 
Mine spends most of it's working life between 3 and 4 thousand rpm, 3 thousand being the beginning of smooth running and four thousand giving about 70 MPH on the highway. If on a slow road, I follow the suggestion in the original owners manual, shift down so that revs rise to 3 k or more to maintain smooth running. Maybe that is why it has always kept the battery up, even with the headlight on.

A friend in the Oz Vincent club has used his Commando MK3 for many years of commuting, managing to put something over 100,000 miles on it during the last twenty years or so, though not without some major repairs. In that time he has gone thru four sprags. He actually kept track of the number of starts each sprag made. He got approximately1600 starts from each sprag. All sprags made it to 1600 but none made it past 1700.
This would be a terrible number for a modern commuter car, perhaps only a year or so of use, but 1600 starts for a fair weather ride is probably enough to see most of us out of bikes and into the electric scooter.

Glen
 
So I guess at 27000 miles my sprag is doing pretty well. I believe the only long trip that has been done on the bike was a trip to Minnesota many years ago. Most of the miles on the bike have been put on at the rallys where it has been used as a loner bike. Jim [now watch it fail next week]
 
He also mentioned that he has only replaced the sprag, not the parts the sprag runs against. This is counter to the info provided on the Norvil site, however it has worked for him. He did say that he changed the sprags as soon as he noticed any slippage.
I know the previous owner of my MK 3 continued using the starter when the sprag was slipping badly and should not have been used. It wouldn't take long to wear out the drive bits with the starting half working /half slipping as it was when I purchased this bike. I wonder how many times it happens this way, where the sprag starts to slip but the owner continues using the starter in hopes that it will miraculously cure itself?

Glen
 
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