Author Topic: Magneto advance/retard  (Read 6473 times)

Online bl**dydrivers

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Magneto advance/retard
« on: 30.03. 2010 23:09 »
Ok Im very confused, I have a Super Rocket, the engine is fitted with a magneto auto advance/retard unit, somebody told me there is different magneto kinds for the auto and for the manual.  Isnt that the gear whats different?  couldnt i just fit a new gear for manual advance?

Can someone help explain this?

Online trevinoz

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Re: Magneto advance/retard
« Reply #1 on: 30.03. 2010 23:34 »
The manual type has a different end to accommodate the the advance/retard mechanism.
  Trev.

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Re: Magneto advance/retard
« Reply #2 on: 31.03. 2010 01:27 »
Hi Trev, which end do you mean?
the tapered end or the end with the cap?

Online trevinoz

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Re: Magneto advance/retard
« Reply #3 on: 31.03. 2010 02:41 »
The points end with the cap, screwed or clip-on.
It has provision via a threaded entry for the advance cable and works.
Trev.

Online groily

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Re: Magneto advance/retard
« Reply #4 on: 31.03. 2010 09:15 »
Sounds as if maybe your fibre pinion has died, from your talk of replacement? Or do you simply want to go to manual because, I think, that's what it had in the beginning?

If the former, bare pinions can be got quite cheaply and new or recon ATDs can too, for a lot more - SRM have them, so I think do Draganfly and some others. If you're going to dismantle your ATD, the only hard bit is getting the tightly-fitted retaining collar on the middle bit of the ATD off (it's behind the gear looking from the outside). When that's done, the thing practically falls apart, and you just have to drill the 4 rivets that hold the whole lot together.

If you want to go manual that would require the different end housing that Trev mentions, plus a different, movable, cam ring to go in. The end housings come in 2 types as well - cable fitting can be at the 'front' or 'rear' of the part, with consequent effect on whether the cable is slack or tight for advance and retard respectively. Usually for an anti-clock rotator like on an A, you'd want the cable on the side nearer the cylinders to give 'pull for retard'. Manual cam rings are different in this respect too - as the notch for the hook on the cable end which moves the ring is in a different place, obviously, depending on whether the cable enters from the rear or the front of the housing.
Doing all that is quite possible, but you'd have to mess with the bearing too. The minimum would be to put the outer race of the bearing you've got into the manual end housing you haven't got, with a new insulator washer, because you can't mix and match bits of bearings and expect long service.

Frankly, if it works as is, you don't want to spend a surprising amount of money on the parts for the conversion when it's all added up, and you're not too confident about playing with the thing, I'd stick with what you've got and if necessary replace the fibre gear.

Good luck!
Bill

Offline 1660bob

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Re: Magneto advance/retard
« Reply #5 on: 31.03. 2010 10:13 »
Hi, might be a howler this, but I have often wondered what the "advantage" (or purpose)is with manual advance/retard. The standard A10 has auto, and so can be ridden and forgot-easy life so to speak. Why, do Super Rockets, Shooting Stars etc. have the manual advance-just seems like something to fiddle with (and get wrong/forget etc). Is it to aid starting? when would you use it? surely not at every set of traffic lights..... Puzzled.... Bob.

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Re: Magneto advance/retard
« Reply #6 on: 31.03. 2010 11:57 »
You have obviously never been in a deep cutting with the throttle WFO working up a hill and the ignition retarded.
Music to the ears.
Bike Beesa
Trevor

Offline LJ.

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Re: Magneto advance/retard
« Reply #7 on: 31.03. 2010 12:10 »
It's a very good question Bob and something that I also have pondered. Understandable on a single cylinder motor to retard while starting so as to avoid kick back but why on twin motors?? And fully retarded in deep cuttings on a 600cc big single un-baffled silencer... Better Still....  *lol*
Ride Safely Lads! LJ.
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1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline MG

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Re: Magneto advance/retard
« Reply #8 on: 31.03. 2010 12:41 »
Quoting from an article about a road test of a Matchless G12CSR (Motor Cycling, May 1961):

"Generally, the control lever for the igniton was left fully advanced. It was retarded mainly for starting and when slogging along, cluth right home, in bottom gear under adverse conditions. This drill applied when 100-octane fuel was in the tank. If premium (95 to 96 octane) was used, then so was the control lever, frequently."

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Online bl**dydrivers

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Re: Magneto advance/retard
« Reply #9 on: 31.03. 2010 13:37 »
The bike as to what it started off life as was a shooting star according to the bsaoc in 1959 and it has a 1961 super rocket engine, the bike is all in bits and is a basket case and every picture i look at happens to be auto advance units and the super rocket i read has manual.  myn has the auto advance unit, i just want to bring the bike upto life as a super rocket to how they were and dont mind converting it to manual as i have to get the magneto rebuilt and restored.

Online groily

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Re: Magneto advance/retard
« Reply #10 on: 31.03. 2010 14:24 »
In which case, no problem at all bdrivers. You need a plain gear (you can get alloy ones and maybe even steel), the manual end housing and cam ring, a cable and a handlebar lever of the correct sort, and you'll be fine. If you're going to send it away for a rebuild, reckon there's a fair chance whoever it goes to will be able to dig up the right bits for you. It won't be cheap though. The parts for a DIY complete rebuild are a good 200 quid retail if you count rewind and condenser, bearings, slip ring, cam ring plus all odds and sods plus the VAT.
If the ATD unit is in good shape, that's very sell-able, and even if it isn't great, there's loads who'd probably pay quite good money for it.
As to 'why manual', I suppose the so-called 'sporting rider' wanted more knobs and levers, like shoving car dashboards full of misunderstood instruments. Silly really. But have to say I have three K2Fs on things, and they're all, er, manual. My only objection to ATDs is the fibre gear, which I think is quite unnecessary.

By the way, if anyone's interested, I'm told a good condenser for a K is apparently Evox-Rifa PME271M622K. It's rated  0.22mF, 300v AC to 110 deg Celsius max with a 'maximum voltage swing speed' of 400v per microsecond. The last bit is, I'm told, important. (Quite beyond me.)  Radiospares, £3.82 per pack of five, +VAT. Compared with Independent Ignition Supplies' £15.00 for one - for an item that some people have criticised in other forums.
I'll be getting a packet for a couple of mags on the bench so will find out one of these days whether they fit the space easily and/or are any good. Does anyone here who understands these things actually know from experience?
Bill

Offline MG

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Re: Magneto advance/retard
« Reply #11 on: 31.03. 2010 16:05 »
groily,

I don't know that particular condenser you mentioned, so unfortunately can't really help you here.
I always use the WIMA MKP10, 0.22uF (microFarad). The version rated for 400VDC/250VAC can easily be accomodated in the K2F armature by using the original bracket (its got 26.5 x 16.5 x 7mm) . The MKP10 are designed for pulse applications and high current ratings, which is vital for the use in a mag. Its just 55 Cents per piece here.
I have found those small yellow condensers that are sold and used from various rebuilders and suppliers in some "rebuilt" mags I have worked on so far. Most of them had failed within very short time

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Online groily

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Re: Magneto advance/retard
« Reply #12 on: 31.03. 2010 23:18 »
Thank you very much for that Markus,
I shall extract the 'small yellow job' I just paid 15 English pounds for and put in the one good spare mag I've got and put in what you recommend (if I can get it). Very much appreciated. Also the bit about 'Vital'. 'Fraid I don't know enough even to know what I don't know in this particular case. More learning indicated.
The little yellow job you refer to and I've got is certainly a miniature object and looks like a stray insect in the drive end recess. It'll be fun unpotting it!
Bill

Offline MG

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Re: Magneto advance/retard
« Reply #13 on: 01.04. 2010 07:50 »
groily,
That's why we have this forum, no need to reinvent the wheel.  ;)

I bought mine from Conrad. Here's the link to the condenser on the Austrian site:
http://www.conrad.at/ce/de/product/459998/KONDENS-MKP10-022F-400VDC-10/SHOP_AREA_17435

There's also a site "www.conrad.fr", but I couldn't find it there. But you could send them an email request with the order no. (459998-62) from the Austrian/German site. If it is available here, they should also be able to deliver it to France I guess.

I hope this is not considered as improper advertisement on the forum? There's just no other supplier in France I am aware of, although I'm sure there are several.

Like I mentioned, I use the original bracket to strap it down and secure it with a drop of superglue.
In cases where there is no bracket (anymore), I glue it in with a drop of superglue to fix it and then fill the recess with epoxy resin completely.

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline LJ.

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Re: Magneto advance/retard
« Reply #14 on: 01.04. 2010 09:48 »
Now you too guys are wetting appetites here and with the costs of those condensers Markus recommends, which look to be only pence. I wouldn't mind having a go with my two spare mags that I have. Now I know Erling has dug into his magneto and had some success, I'm wondering if I might also be able to have a go, seems that the magneto inners are the last taboo places of the A10, I 'd love to conquer it. How difficult is it in getting one of these condensers changed?? I hear that it lives deep in the centre of the windings, is there real risks of damage?

The one thing that would concern me is which way round would that condenser go? lol. not a good start eh? Should I leave well alone?
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red