The 850 MK3 starter motor (Prestolite and its clones)

Thanks for sharing this with us all.  I'm sure there are a lot of members who make useful modifications that need sharing for the benefit of other members.  Perhaps a new category could be created in the Technical section for members to add their own ideas.

Well done.

Hi Peter,

I would be very interested in this modification to the 5780BN starter motor for my MK3 rebuild. You said M&P had these, is this still the case as i cant find them now ?

Kind regards,

Ian

I found your 2016 post on the this subject: https://www.nortonownersclub.org/node/3337

And I have to say the prospect of removing the kickstart is very appealing (I'd like to move the footrests back without going full-on rearsets). Has your confidence in the starter motor mod stood the test of time?

Hi Peter,

Interested in reviving my 850ES's ability to start on a button. Knees clapping out. Have a belt drive and no starter at present but have all original clutch/drive etc stuff to revert to original.Happy to do that soon and i was looking at a Wosp starter but your post has led me towards your route. Obvious financial gain (to be spent on other bits of course). Reading your post correctly, i hope.

Looks like i need to mod shaft bearing. Commercially available and no prob. You indicate a change of starter pinion needed. Are you suggesting using one of original starter which i would prefer not to do or obtaining a new one? Are they commercially available? 

Thanks

John 

Hello Peter SHAND, we met during the inter rally in Austria, on a parking lot where there were several bikers parked a green space and a small shop, it was on the road going towards the iron mine. I recognized your name on the support of the footrest, which I had taken in photo.

Thanks for that Peter.

Apparently my starter motor has the Harley 4-pole guts (Andy Holmes did it and I later bought it back). It currently serves only to fill the hole. Remembering how "well" they worked originally, I just use the kickstart. But being able to remove the k/s lever changes the calculation entirely. I'm going to look inside my starter to see what I've got and it's very lilkely I'll be in touch.

One more question if I may: your 2016 article describes a modification to the starter gear for the sprag clutch in which you cut down a needle roller inner race (like these https://www.wychbearings.co.uk/needle_bearing_inner_rings.html ). Given the amount of metal you remove, surely you've gone thru the hardening and lost the precision ground surface. Wouldn't it be more direct and just as satisfactory to turn a bit of EN8 (or EN24 if you're feeling flash) bar to size and heat treat that?

Rallye international Norton 2018 en Autriche | Flickr

Peter,  did you receive the PM I sent you. I can't find it now. I've no idea how the pm thing works. !!

Cheers. Hans.

If you refer to my nippondenso based dynodave/atlantic green  item, Here is the difference. All the prestolite style mods still have the same armature. This prestolite armature is a SINGLE layer wrap. Of course the added brushes and coils will help "some".

Yet the ND two layer wrap armature provides a measured 40% increase in magnetism per amp of current draw. I have never seen a twin wrap armature for the prestolite or its clones. So to me, even the upgraded prestolite design continues to be inferior after all that work. I own a NOS prestolite that works just fine on my MK3 with a good charging system....

Since 2004 I have personally built and sold over 1300 of mine with extremely few complaints. While I should be honored that WOSP has stolen my design, I still can sell mine as I have kept my price the same since day one but WOSP has just gone up 10% ..

Does WOSP know anything about a NHT commando MK3? and  give phone support?

I own 4 of them, one as a complete basket case from parts I assembled and made running since 1995 and one with 5 original miles/never registered or driven.

One thing I do recommend is a better charging system over a starter. It does not matter how good the starter is if you run a constant semi charged battery.

A tiny slimline featherbed battery , a regular commando battery and a pure stock MK3 battery will all start a commando if fully charged.

The main reason I was asked to do my starter was for the rusty destroyed armatures that were not available since prestolite discontinued support in the mid 80's.

$375 = £285. Plus shipping and taxes.

https://atlanticgreen.com/starter.htm

I found the details of the 06-4791B starter some while ago. And it reads very well. NipponDenso internals, gearing reduction thru 9 tooth pinion and lighter too. But Peter Shand will fix up your old Prestolite far cheaper and, on the evidence we have, it is plenty good enough. Maybe squeeze in a 20Ah battery if it's a bit reluctant on cold mornings.

Well I,ve just replaced my WOSP starter. New in 2019, it blew up after only 13,000 miles last month. The commutator disintegrated on startup and the sudden stop broke my reliable Aliexpress sprag, luckily with no damage to the engine sprocket or the starter drive gearwheel. This is my third failure of this type starter motor although none appear to have genuine Denso motors as the original Dyno Dave version.

Previous starters of this type from Norvil and RGM have both failed in service, the RGM under 10,000 miles with blown armature windings and a badly worn drive pinion. On a Spanish trip the Norvil started the bike OK then instantly turned into a 60,000rpm electric motor which blew up with a big clunk.

In all cases I managed to get home on my e start only Mk3 with the help of hills or push starts.

I,m not remotely interested if an armature is single or double wrapped, how much magnetism it has or whether the vendor knows anything about Mk3 Commandos. I just want a starter that works like on my Japanese engines. The Norvil and RGM models are no better than the WOSP version in my experience, in fact they,ve both failed at a lower mileage.

Bottom line is these are not up to the job on my bike so I,ve had my original Prestolite armature and commutator rebuilt by Robson and Francis. It,s now fitted to a new 5780BN four field coil case and brush set using the original end caps. The front drive side has the original bronze bush which is still a perfect fit, the rear I fitted with an needle roller and inner ring back in 2008.

Hopefully I,ll have a starter that,ll outlast any of the pricey Dyno Dave type which are close to £500 these days from RGM and Holland Norton Works. The WOSP is better value at around £300 but a similar unacceptable working life.

FWIW the only blown up armartures I am aware of, are from a sprag flip over lock up. No armature can withstand 35,000 rpm.

per NW " The commutator disintegrated on startup and the sudden stop broke my reliable Aliexpress sprag, luckily with no damage to the engine sprocket or Peter Shands excellent sleeved gearwheel mod. " 

You should note the sprag failure lockup is what causes the motor to spin up to explosion. not the other way around you describe..

The motor alone has not blown up from it's own unloaded free wheeling RPM. However all motor manuals suggest a maximun of 20-30  seconds of continuous cranking use with an adequate cool off period before reuse. ANY STARTER  The commutator will likely fail if super heated mercilessly.

Strange you brits have so much trouble? here in the US a lifetime warranty is almost never needed or used .   Sprag lockups are somewhat rare, but do on occasion happen.  A rebuild at minimal cost is provided.

On sprag blow ups, I request examining the 3 components and they are almost always extremely degraded leadiing to what I call "slip[ and fall" of the sprag dogbones..

US price high? sorry now you know how we feel getting your parts....

P.S. I NEVER sold one of my starters to RGM....

In the interests of informed discussion, I'll add a comment here.

I have no direct experience of the DynoDave starter, only what I read on the Atlantic Green site. My main experience of the Prestolite starter is from the original setup some 40 years ago when I just gave up and used the kickstarter. But using those 40 years of accumulated knowledge I have now built a bike with the 4-pole internals, mini solenoid, heavier cables and 16Ah battery - which seems to work ok. And I'm minded to have Peter Shand modify it so it's reliable enough long-term to remove the kickstarter.

Doesn't have to spin up like a Honda, as good as a BMW R100/7 will be fine (a bit sluggish at times even with a 25Ah battery). And that leads me on to the NipponDenso option for the BMW (apparently based on the motor fitted to Toyota pickups). You can have the original Bosh starter refurbished for £110 or you can buy the ND replacement at £329. Of note is the use of planetery gearing so that the motor spins quite a bit faster, does actually crank a boxer twin like a Honda and is reported to be superb.

I don't know what £285 plus shipping and taxes will actually translate to when it arrives on UK shores, perhaps you might enlighten us David. But it's in the ballpark of the BMW item and, if it really does transform an £8000 Commando, not outrageous. More to the point, the Bosch starter started a BMW fine in 1976 and refurbished one will go another 40 years so why spend more, although clearly some do. But restoring a Mk3 to how it was in 1975 is hardly desireable so some modification is definitely needed.

I agree with your point about the sprag clutch being the likely culprit in spining the starter to destruction and a Prestolite would be similary wrecked. And there is a case to be made that spinning the motor "with vigour" will actually give the sprag a slightly easier time.

For me, the jury's out, but I will go the Peter Shand route because 1) Peter has been very open about his changes, sharing the details so anyone so minded could do it themselves and 2) it is cheaper.

For information, my original replacement starter was designed at the request of a friend with a MK3.

His motivation was an expensive "rebuild" sent to California for a 4 brush/coil up grade. It cam back running the wrong direction, At further local cost to fix that problem it final worked. We ended up taking it apart to discover the starters actual internal condition. The condition of the core and rebuild was rather poor and not close to the price of all the work done.

In the final analysis the lack of real prestolite replacement parts, specifically the armature, was the motivation to move forward. Prestolite new components were terminated around 1985 and all inventory of Norton starter parts was liquidated. It would appear" British Only" in Michigan bought a large amount of the inventory. In 1994 British Only was selling NOS complete starters and I bought one. to use on my own basket case MK3. For 5 years/seasons I rode with a pure stock (except Lucas Rita) bkie and it was fine and always started and ran. The first YUASA battery finally died and the bike was pushed aside.

In 2004 the new starter issue was raised and my friend wanted something better so began the ND replacement to overcome parts unavaiIability.   In reality my starter, if real nippondenso part were used, if available,  the starter would likely cost $1000.

So the current prestolite "upgrade" is doing  it's job using chinese arnmatures (probably) .

Here in the US, for retail price, wearing armature gear could receive a new armature for the cost of mail. In europe,  the dealers probably make more money than I do as the builder.

Your british woap starter probably uses similar chinese parts. You get a 1 year(1 season) warranty?

So after 18 years and 1300 of my bolt in starters, conversion for your starter is still based on currently available harley chinese parts and lots of hand craftsmandship.

Interesting that both my clutch rod seals and starters were offered to NOC but "crickets" was the answer?

Good Morning Peter,

My starter sometimes works but more often just makes horrible noises, I suspect the bushes are worn as there is a fair amount of play apparent, please could you contact me regarding purchase of one of your modified starters?

My email is timm.nicholls@googlemail.com

Thanks and regards.

Tim.

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HtH

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Hi Peter,

Being a new member it was interesting to read the upgrade you can do for a MK3 standard starter motor,as i have bought a new 4 brush Prestolite motor how can i have this upgraded with a the bearing fitted to the front plate,could you help?

Many thanks Graham davis.alison04@gmailcom