Misc: Ignition Lucas KVF Magneto on a Rapide with manual adv./ret.

[Robert Watson]

Think of it this way Peter

With an ATD the spark stays in the same place relative to the armature, and the advance gets moved between the output shaft and the gear of the ATD. With a manual advance the spark position gets moved around the armature, changing where the mag must produce the spark.

 

[Peter Holmes]

Hi Peter, yes what you say is correct nothing changes inside but the armature has an optimal sparking position and one cylinder is on it and the other isn't. But by moving the advance/retard from before the armature to effectively after it you worsen the situation.
So say the auto unit moves 15 degrees the optimal spark is in the same place whether advanced or retarded.
But with a manual adv/ret you move the spark away from it's optimal position by 15 degrees, the real problem is the other spark WAS 25 degrees off optimal already and now you have moved it a FURTHER 15.

Chris, If Lucas supplied these manual magneto parts would they not have taken this problem into consideration and supplied the slip ring with the operating slot in the optimum position in an attempt to split the inadequacies into equal amounts, rather than have one spark 40 degrees from optimum.
I really struggle with anything electrical. If you cannot move the slip ring to an optimum position, does it follow that every manual magneto ever fitted to every configuration of engine was not operating at its optimum, or is this something that only effects the 50 degree V twin split.

I really appreciate Roberts attempt to educate me, but you must take into consideration that you are dealing with someone that has to check the rotational arrow on a tyre an inordinate amount of times before I fit it, just to make sure that after huffing and puffing for what seems likes hours, I don't find when spinning the fitted wheel it is not rotating the wrong way, what hope have I got of understanding the intricacies of a manual magneto.

Michael, I am sorry but I cannot answer your question, for some obscure reason that I cannot remember I decided that I wanted a manually operated magneto, so had one converted by Tony Maughan, but then I changed my mind and had it converted back ATD operation prior to fitting it.

 

[Bill Thomas]

A mag. For a V Twin is a Bodge.
I have done many bodges.
Some better than others.
The manual thing was done for a single really I think.
But even Mr Vincent went for a Distributor
With the D. In the last Vincent's.
The trouble is you need good electrics.
Which we can now do with the Walkernator.
Just Wish I knew more when I was
Younger and raced the L ning.
But I still use a Mag with manual on the Comet.
Cheers Bill.

 

[A_HRD]

Well, in my near 50 years ownership of my C Rapide, and in the years I used to go to all the Continental rallies and many UK ones over a couple of decades, I always had a manual KVF magneto. I much preferred it to the ATD - which often caused me problems. I love to be in control of my engine with more than just the throttle. I particularly liked to have the ability to ease back slightly on full advance when slogging up long gradual inclines on motorways/autobahns/interstates 2-up with camping kit too, against the wind, when I could feel/hear the "pinking" start. In short, just like Marcus does, I listen and tweak my engine according to conditions. It takes years to get that 'feel' but in my opinion it pays dividends. Perhaps the fact that I have never holed a piston has something to do with that? Who knows? Moreover, my Rapide has always been a 1st/2nd kick starter and what's more I won 'slow running tick-over contests' at rallies years back!

The only disadvantage to me was the need to drill a hole right through the middle of the mag cowl to feed the adv/ret cable through. I've got pics somewhere but can't find them at the moment. I'd say to Michael, if manual adv/ret floats your boat - go for it. But get a repro mag cowl and drill that - not your original.

Peter B

 

[Chris Launders]

I have manual adv/ret on my Brough Superior (not that there is a choice) which is twistgrip operated and is wonderful to use, but being a 60 degree V means the 2nd spark actually fades so much disappears at kickover speed when fully retarded so it has to be started fairly advanced.
Being a side valve this is not too much trouble and once running can be fully retarded when required though is still a little erratic at tickover.

When I got it the magneto was sick so to get it on the road I built a coil set up with auto advance. With this fitted it would start just leaning on the kickstart and tick over unbelievably slowly but again like a Vincent it lacked a good reliable charging system. I'm tempted to revisit this now having a reliable dynamo.

 

[Black Flash]

Well, in my near 50 years ownership of my C Rapide, and in the years I used to go to all the Continental rallies and many UK ones over a couple of decades, I always had a manual KVF magneto. I much preferred it to the ATD - which often caused me problems. I love to be in control of my engine with more than just the throttle. I particularly liked to have the ability to ease back slightly on full advance when slogging up long gradual inclines on motorways/autobahns/interstates 2-up with camping kit too, against the wind, when I could feel/hear the "pinking" start. In short, just like Marcus does, I listen and tweak my engine according to conditions. It takes years to get that 'feel' but in my opinion it pays dividends. Perhaps the fact that I have never holed a piston has something to do with that? Who knows? Moreover, my Rapide has always been a 1st/2nd kick starter and what's more I won 'slow running tick-over contests' at rallies years back!

The only disadvantage to me was the need to drill a hole right through the middle of the mag cowl to feed the adv/ret cable through. I've got pics somewhere but can't find them at the moment. I'd say to Michael, if manual adv/ret floats your boat - go for it. But get a repro mag cowl and drill that - not your original.

Peter B

Hello Peter,
I fully agree with you, but your advise to buy another magneto cowl in order not to drill the the matching number one, but is a very expensive advice too.
But then maybe it is better to spent our useless Euros before the ECB goes bang anyway, thanks to madame inflation (or was is lagarde?)

 

[MichaelOrgzey]

Cheers for all your replies. I'm happy with my manual advance on my pre unit Triumph for the same reasons Peter B. likes it. But then the internals work in favor for a parallel a Twin, I just wasn't to shure with a 50 degree V Twin.
So it does seem to boil down to personal preference which is good to know.
Happy new year to everybody!

 

[highbury731]

A while ago there was some talk about the SR1 magneto, which has a rotating magnet poles 25 degrees apart. Should it be possible to convert to double sparking, that would give full spark power to both cylinders.
So
- can a SR2 plastic pickup housing be fitted, and
- a points cam with two lobes with one offset by 25 degrees be achieved?
- is the SR series able to be converted to manual timing (not needed on a Vincent twin)
- how to obtain a flange mounting conversion
- have to make a magneto cover, probably in grp

 

[bmetcalf]

SR mags have been mentioned here before, but “SR-1” is too short for a search. Maybe Graham or some other wizard can find the thread(s).

SRs were available with manual control. I have info at home and can post on Friday.

 

[LoneStar]

“SR-1” is too short for a search.

True, an unfortunate "feature" of the forum software. You can't search for 'NGK', '289', 'KVF', etc.

But here's a workaround:

- Go to Google advanced search ( https://www.google.com/advanced_search?hl=en )
- Enter 'https://www.vincentownersclub.co.uk' in the 'site or domain' field
- Enter your search term, and proceed.