Sprag

I am an enthusiastic reader of this forum.
Have planning to get the starter on my MK3 to work. I have changed spragen once, it went bad. I have a 4 pole starter with new cables and tri-spark ignition.
I read here in the forum a while ago that there was one out there who had a more robust sprag solution
This, I am very innteresert in trying.
Can anyone help me to get in contact with this supplier.Angre
Vidar

Mk 3 Commando

Postby Norton Dave » Thu Dec 22, 2011 3:13 am
Hi to every one Merry Xmass and New Year I like to read this site , there are a lot of smart people here with good advice , and some dick heads but you get that in life . So Iwould like to ask does any one out there know how many MK3 Commandos were produced in the first factory run from 1975 till 1977 starting with engine number 325001 , before the short lived re birth . I would like to know how many genuine original as it seems to be important here MK3 were produced . By the way my replacement sprag cluch is still working so will be posting them on EBay soon in the new year if there was a number of people here interested Ithink I could sell them very cheap and I think they are better than the Renolds and it has one more roller got to be better , keep safe over Xmass Norton Dave .

Norton Dave

Posts: 5
Joined: Sat Jul 09, 2011 9:53 pm

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This might help, though I'm sure there'll be others. If the sprag keeps failing perhaps the bore in the engine sprocket is worn.

Cash

I have recently started studying this sprag problem with a much closer look. While I don't have a full blown report ready yet, my observation so far are that the inner race on the drive gear shows many more instances and larger deformations, rather than the ID of the sprocket. I only have a half dozen samples to study from so it is not conclusive. A few of the sprags show "wear" on the ends of the dogbone/rockers .

more to follow...

The inner race is a joke and the whole assembly collapses on itself after asking it to turn over 828 c.c.s of cold engine. Reminder that this is an electrical assister system and was meant to be judiciously employed in conjunction with the kicker. At the same time, same moment.

I guess I take a different view on the E-Start. I bought my MKIII entirely as a investagative example. I found the 2 brush start to work just fine for 5 seasons on the same battery, the factory specified yuasua battery. It worked virtually flawless for the whole 5 seasons until the battery died.
On the next major maintenance I will install a gearbox cover with the kicker eliminated...though I will be installing one of my starters and the 3 phase alternator since I believe the charging system to be inadequate.
True they are not up to modern bike product standards, but heck, if I can make it work then why not everyone else?

Just read about the sprag issue. My sprag was cracked when I removed it recently. After a few days of web investigations I found out that the sprag gear on the Royal Enfields with the E-starts are the same as the MK3. Same manufacture's part number, but they are the older 14 roller type---but a lot cheaper than getting one out of Norton.
You may want to do your own research on this to back up my findings---just to make sure.
I'm sure that if they are the same ---this will get passed around quickly and the price will escalate as the demand increases.

I just stripped my sprag a few days ago, so I am in the market for one too.

It is just over a year old and I have been using the electric start exclusively. But when I went to start the bike last week, the battery was low, and I forgot to flip on the choke. After a few attempts at starting the battery was weak, and the low voltage to the Boyer (analog) caused a backfire while I was using the starter - bang went the sprag.

Shit - I've known for some time the danger of a backfire with low voltage to the Boyer, and what it could do to the sprag, but I guess I expected it would never really happen. Dyno Dave - I know, I know - I have read your warnings. Ignored at my own expense.

This time when I replace the sprag, I will replace the Boyer with an electronic ignition which is more tolerant of low voltage (TriSpark, etc.).

Anyone with a line on a unit more robust than the 18-tooth model currently available - please let us know.

Norton Dave - tell us about this replacement sprag unit you referred to ......

Yes, Dave Norton.
We want more ...
Tell us more about the new robust spragen

Vidar

Sorry that little mistake.
I meant Norton Dave.
It is my Googel translator who want it that way
Vidar

Sorry for the delay responding been away with work , about the new supply for sprag clutch I would like to do a hardness test on the rollers to see how it compares to the old renolds units . As I posted a little while back I would like to be sure about there quality first before offering for sale . As to the many peoples views here as to the reasons for there failures , well I believe all things being equal IE , battery plenty of charge, starter wires up graded both the inner drive sproket and outer gear crank in spec then you do have a working electric start , I do not agree with the electric starter assist stories . So as not to get involved with the politics as to chicken egg stories of did the sprag cause the problem or did the low voltage ignition , bad timing overload backfire mechanism not working etc. let me say I just wanted to source and offer a cheaper and better alternative to what is about at the moment not to re engineer the bike . But that would be nice , some say the new starter with more power is the way to go , but does that put more stress on the whole affair , finally resulting in a premature failure of the sprag . Like to know how long these new starters can opperate before the sprag fails . Sorry got side tracked hopefully this week I can do some hardness testing then I will upload some pictures and show the results Norton Dave .

Old Renolds units? We haven't sold those for years! Our current ones have a more substantial cage, and a friend of mine just pushes his button and off he goes on his Mk3. Which he uses as an everyday bike, not a museum piece, in all weathers. He does have two dry cell batteries, though, so the most frequent reason for the poor sprag to fall to bits- low current, hence electronic ignition backfiring and destroying the sprag through sudden overload in the wrong direction- does not occur. Can't remember selling him a sprag in many years.
Joe Seifert/Andover Norton

Sorry ZFD did not wish to infer that you sold old Renold sprags , regardless if the sprags are Renolds , Borg Warner Steiber etc etc I just was interested how much longiverty you can expect from running the new type starter motors to the MK 3 . I also ran a standard 14 tooth Renolds spag as fitted by the factory in my first MK3 brought back in 1977 and it lasted 10 years with the original Prestolite two pole two brush starter . I thought that was good . And it was a work bike which I rode in all weather conditions , because it was my only trasport . Do you happen to know the brinell hardness of the sprags you sell thanking you Norton Dave .???

Norton Dave said:

I do not agree with the electric starter assist stories.

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But, how many times have you used your Mk3's electric starter after the bike has been left out all night in temperatures well below freezing and you've had to scrape half and inch of frost (or inches of snow) from the seat?
Most owners would not consider using their bikes under those conditions now, however, back when our Commandos were new (in the good old days!) an owner would often be left with little choice than to do that if they wanted to get to work on a dark frosty winter's morning.

Good to hear from you Dave
Is excited about your results. That mean that you have the resutatet within a week or two.?
It fits the case well. I have now started to dismantle the starts system, and will order new gear and sproket wheel, so the starting point my being opptimalt.
Vidar

No idea about the hardness of our sprags, to be frank. All I know is that the one on my friend Franzi's bike works and to answer LAB's post- when I am sitting smugly in my shop with freezing temperatires outside and the occasional snow or cold downpour, and I hear a Commando outside, it is ALWAYS my friend Franzi with his Mk3 850, if he isn't on his Norton "Classic" Rotary. Mostly the Mk3 in winter, though. And it always starts when he presses the button straight away. He has the Heavy Duty starter lead conversion on it (part#06-7269), but I am not sure if he has or hasn't the 4-brush conversion.
Joe

ZFD said:

when I am sitting smugly in my shop with freezing temperatires outside and the occasional snow or cold downpour, and I hear a Commando outside, it is ALWAYS my friend Franzi with his Mk3 850..........And it always starts when he presses the button straight away.And it always starts when he presses the button straight away.

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Outside your shop? When the engine is already warm? It's not surprising then.

ZFD said:

He has the Heavy Duty starter lead conversion on it

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Non-original = Doesn't count.

ZFD said:

but I am not sure if he has or hasn't the 4-brush conversion.

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It certainly wouldn't count if he did.

Electronic ignition? I bet it has a modern high CCA battery too? Left hooked up to a battery tender when not in use? In a nice garage?

Luxury!

LAB,
I have seen him start the bike from cold, too. His garage is unheated by the way- sounds as if your bike(s) lead a pampered life by comparison!

If you aren't satisfied with the test conditions, come here and test it yourself! If you can stand the cold and the snow, that is.

Not sure what the leads to the electric starter got to do with the life expectancy of the sprag, though. Non-original? Even the sprag these days is non-original because the original sprags as in a 1977 Mk3 from new had far flimsier cages. I think the main advantage his sprag has- and why it lives so long- is that the Boyer has 12V to play with even while he pushes the button and therefore does not go into erratic firing mode.

Joe

ZFD said:

LAB,
I have seen him start the bike from cold, too. His garage is unheated by the way- sounds as if your bike(s) lead a pampered life by comparison!

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I wasn't necessarily referring to my own bikes-only the general conditions under which most "classic" bikes seem to be kept these days (heated garage/trickle charger/etc.) even an unheated garage is a luxury when compared to "the good old days".

ZFD said:

If you aren't satisfied with the test conditions

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It's not a case of being satisfied or dissatisfied, my point was that an old bike that's been fitted with modern upgrades will no longer be a typical example of how that bike performed originally-therefore any modern day "test" results are meaningless.

ZFD said:

come here and test it yourself! If you can stand the cold and the snow, that is.

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I'm a bit busy, could you bring it here? (Bring your own snow)

LAB,
A mate bought a late absolutely bog standard Mk3 except for an analogue Boyer ignition about six years ago. If the battery has enough charge the bloody thing starts on the button 99% of the time. When it kicks back there's a mechanical clank and it keeps on cranking. It is most annoying as we all told him Commando starters are crap :shock:

I suppose it could be haunted, as leather jacketed street corner yobs, I kid you not, one of the lads had a C11g that would sometimes fire up when the ignition was turned on and we all reckoned that was.
It took us a few years to fathom out why.

Cash

cash said:

A mate bought a late absolutely bog standard Mk3 except for an analogue Boyer ignition about six years ago. If the battery has enough charge the bloody thing starts on the button 99% of the time. When it kicks back there's a mechanical clank and it keeps on cranking. It is most annoying as we all told him Commando starters are crap

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Well, that's hardly surprising, as my own Mk3's upgraded Prestolite starter is reliable (except when the sprag disintegrated!) and with its AGM battery, it turns the engine over with ease - but I doubt it would perform anywhere near as well down below freezing point after being left out in the open all night.

Even the owners handbook states:

For the first start of the day and particularly during very cold weather, it may be necessary to turn over the engine several times using the kickstart pedal to break the oil film before using the electric starter. Alternatively, the electric starter can be supplemented by the kickstarter.

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