The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Superflash on 27.10. 2020 00:30

Title: Manual Magneto
Post by: Superflash on 27.10. 2020 00:30
Hi all,

Just wondering if I can use a K2F Model 42230 unit in the A10? According to the Lucas parts list, this is for a 500cc/600cc AJS. However, when you compare the individual parts from the 42230 to the list for the correct BSA mag, they are more or less the same.

I was going to use an ATD magneto, but have decided to run a tacho, which means of course I have had to look at the manual mag. The bloke at Britcycle here has a 42230 mag for a reasonable price. Less all the control bits of course, but that can be sorted later.

Title: Re: Manual Magneto
Post by: Black Sheep on 27.10. 2020 06:33
Not clued up on K2F model numbers but essentially any K2F will fit. There are one or two oddities but if it came from a bike it will fit a bike.
Bear in mind that many K2Fs are now an assembly of mix 'n match parts.
The other thing is that for a manual K2F, the body needs to have 3 tapped holes to retain the slip ring housing whereas the normal auto advance one just has two.
Title: Re: Manual Magneto
Post by: Swarfcut on 27.10. 2020 07:49
  To add to BS on mix'n match.   "Proper" A Series BSA Magnetos have a flat machined on one lower corner of the body to give a clearance between the  edge of the cylinder base flange/crankcase  and the magneto body. Three hole body used for manual mag can be used with some  two hole auto points housing as a straight swap. To go the other way needs  the extra drilled and tapped hole. If the magneto body fits the motor, the magneto can be built up to suit. Pitfall with points housings is that they do not interchange between curved (standard) bodies and straight sided (competition) type. To misquote  Michael Caine,  "Not a lot of sellers know that"

Title: Re: Manual Magneto
Post by: JulianS on 27.10. 2020 10:06
Showing the K2F body with machined flat to fit the A series crankcase.
Title: Re: Manual Magneto
Post by: Black Sheep on 27.10. 2020 10:14
Didn't know that! Anyway, my A7 and A10 mags don't have that but still fit...
Just back from a test ride on the Star Twin with the rebuilt mag. Going beautifully at last. It's been 2 years since it started giving problems. A bit of a saga.
The mag rebuild involved a body swap - no machined flat on either.
Title: Re: Manual Magneto
Post by: JulianS on 27.10. 2020 10:33
This one shows how tight the fit can be. If there is not enough space the mag will not seat square on the case and give an instant oil leak and stress on the bearings and pinion.
Title: Re: Manual Magneto
Post by: groily on 27.10. 2020 13:46
Have often wondered if they were tighter to mount on some versions of As than others without the milled edge. But it certainly helps get the long nut on from the cb end. That said, I'm running a non-chamfered one on my A and it goes on easily enough.
Are there any subtle differences in crankcase design over the years which could affect it, eg, plunger vs s/arm? I have absolutely no idea, but will stick my neck out and say I have never (yet!) had a problem getting any K2F onto a s/arm machine. But it is nice to be able to find one with the chamfer for Beesa owners all the same.

Ref the umpteen versions of cb end housings, and the pix and comments various - there are as  Swarfy said  auto end housings whose 2 holes screw in top right and bottom left - which is what you want if swapping from a manual one with left hand cable entry (and no threaded hole top left on the body). But care is still needed - there are also  housings drilled for attachment at top left and bottom right, in which case you still might have to get drilling.
Title: Re: Manual Magneto
Post by: BigJim on 27.10. 2020 13:49
Have to admit i ran a file down the edge of mine to give some clearance! Seems to be ok at mo, no signs of cracking. Mine is the squared off one and assume the inner timing cover is out of line somewhat. Now have a similar gap as shown on Julians photo.
Title: Re: Manual Magneto
Post by: chaterlea25 on 27.10. 2020 21:49
Hi All,
The chamfer was something I did not know about until I went to fit a BTH mag back in 2009  *ex* *ex*

Title: Re: Manual Magneto
Post by: Superflash on 28.10. 2020 00:25
Thanks for the feedback. Rather than adapting my current mag to manual advance, I was looking at consigning it to the spare parts box, and buying this one. My only hesitation was the fact that it's advertised as being suitable for AJS/Matchless twins. Just reading through the various threads etc, I'm going to take it on faith that with a little work, it will fit.... famous last words..... Cheers
Title: Re: Manual Magneto
Post by: groily on 28.10. 2020 07:45
I thought that sort, with the alloy dome, was also used on some early 50s / mid 50s Beesas too? May be quite wrong, but have certainly seen a few fitted on them as well as on AMCs. If I had all day I could check the Lucas parts lists of 'Equipment specification by machine' - but then, so can any interested party!
Title: Re: Manual Magneto
Post by: Swarfcut on 28.10. 2020 08:39
 Reckon you're right there Mr G. Thanks to the parts lists published on the excellent Brightspark Magnetos website, I found the body on my original 1953 K2F Auto Maggy on a Plunger motor had started life on an AJS twin. Ariel Huntmaster type is another variant often substituted, and has no flat.

 If the body clears the crankcase, or as Big Jim did, made it fit, then you will end up with a runner. Conversely a proper champhered BSA body stands a good chance of fitting any other make and model. You wonder why Old Joe did not machine all bodies with the flat, the answer nodoubt being the penny pinching cost of that operation.

Title: Re: Manual Magneto
Post by: Superflash on 28.10. 2020 09:59
Thanks guys. I did do a bit of research in the Lucas catalogue and all the internals look to be the same. I liked this one as it closely resembles the stock maggy for the Super Flash. Can also pick up the pinion nut with tacho drive easy enough. Only thing left to hunt down is the triplex primary drive. So duplex will have to do for the meantime. Cheers
Title: Re: Manual Magneto
Post by: RDfella on 28.10. 2020 13:13
SF - never been convinced about triplex chains on a motorcycle. Unlike machinery where axles are normally supported at both ends, a motorcycle gearbox mainshaft is unsupported at the outer end and thus will flex, if only by a small amount. Under load, this will mean the inner row of chain will take the most load, the middle row slightly less and the outer row probably none at all. Meaning, as far as we're concerned, a duplex will likely take as much load as a triplex.
Title: Re: Manual Magneto
Post by: Black Sheep on 28.10. 2020 15:26
Agree with RDfella. Why triplex? If my 745cc Norton Atlas is fine on a single row primary, a triplex chain seems like overkill. The duplex on my Star Twin is still the factory original 60,000 + miles on. Good enough for me. 
Title: Re: Manual Magneto
Post by: Superflash on 28.10. 2020 19:48
Perhaps in 1952 Mr. Hopwood thought a triplex chain might make the Americans go "oooh ahh"? But you're quite right. From a mechanical point of view a duplex setup is more than adequate. Given I'm not going to use the original SF carb, I probably shouldn't get too hung up on the chain? Cheers
Title: Re: Manual Magneto
Post by: Rex on 29.10. 2020 08:37
That era Indian Chiefs had a quadraplex chain fitted. Doubtless a single row chain "would have done" the job but longevity was the aim.
I'm rather sceptical that a triplex clutch will tilt on it's mainshaft enough to make any difference to a triplex chain though.