The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: coater87 on 01.05. 2009 01:34

Title: auto/manual magneto
Post by: coater87 on 01.05. 2009 01:34

 Can you simply add an auto advance unit to a manual magneto? Meaning, are all K2F magnetos the same as long as the direction (clockwise/counter clockwise) is the same? I have come across a K2F with a funny kind of "pipe" sticking out of it near the points cover, it has great spark- and I believe this pipe thing makes it a manual. My own mag has no such fitting, but has about 50 other problems including a broken case.

Title: Re: auto/manual magneto
Post by: a10gf on 01.05. 2009 01:47
Looks like this picture ? (I just have the mag in front of me, planning repairs). The pipe is for the cable to the ignition control handlebar lever. You can use it in auto mode. With the advance\retard mechanism parts + spring intact inside the points housing the camring will be in full advance (there is also a provision for locking the camring with a screw). So (unless I am missing something crucial), with no control cable fitted, just use an auto advance unit, set the timing as usual, and ride away.

Title: Re: auto/manual magneto
Post by: groily on 01.05. 2009 07:20
Yup, the guts of the things are the same.
The cam ring should indeed be locked in the full advance position as that's the best spot for best spark.

However, it's relatively easy to swap the end housings over between mags to preserve the same look as before. The only sweat is the casing would need a hole drilling and thread cutting to hold one side of the auto-style cam ring housing, as the screws go into different places (the 'pipe' thing gets in the way at top left). The alloy outer cover with cut-out button in the pic uses different fasteners - the differences are obvious and all threads male or female are 2BA. Only other thing would be the need to swap bearing outer races, and set the end-float up on the armature (as a different housing may require shimming/un-shimming).

Another option is to use the manual mag as a manual mag (as per Super Rocket etc. . .) Just needs a cable and lever for the A/R, and a plain pinion instead of the fibre thing and ATD. SRM sell alloy pinions. I've put one on mine and I far prefer it, not being a fan of fibre pinions.

If your manual mag has a screw-on end cap and 2 screws for the HT pickups instead of the clips, and smaller holes for the pick-ups in the body of the mag, then it's a K2F'C' - for 'competition'. But otherwise exactly the same, with the advantage that a kill button can be run from the central carbon brush in the screw-on end cap, whereas in the case of the one in the pic here, it's a Q of having to press the tit to stop the engine.
Title: Re: auto/manual magneto
Post by: LJ. on 01.05. 2009 08:58
If your manual mag has a screw-on end cap and 2 screws for the HT pickups instead of the clips, and smaller holes for the pick-ups in the body of the mag, then it's a K2F'C' - for 'competition'.

Which is not a 'Kentucky, 2 Fried Chicken' job  *lol* *lol* *lol*

Seriously... Noticing the end cap and kill tit button on this particular magneto, similar to whats on my 49 Star Twin... can anyone think of a way to divert the switch to handlebar and keeping this end cap? Obviously some modification would need doing internally. I've thought about this but no lights shine in my head on this one. The reason is because of a fear with sticking carbs or any other such emergency. I recently had a screaming engine because of a sticky and gummed up throttle cable and by heck you wanna kill the engine as quick as you can when that happens. Not so easy bending down with left hand pulling in clutch and reaching over with right hand, all at 60mph!  :o

Appologise to Lee, I've just realised I've hogged his thread
Title: Re: auto/manual magneto
Post by: roadrocket on 01.05. 2009 10:57
Answering Lee's question (you did steal the thread...  *smile*): I have this modification, I had the mag overhauled, and the good man doing it, turned a housing for holding a brush in some sort of plastic. It took him 15 mins. to do, but he is clever. The rest is just a wire, and the button available from dealers. Can take photos if you like.
Title: Re: auto/manual magneto
Post by: groily on 01.05. 2009 18:08
yes, you just need a carbon spring loaded brush which touches the top of the cb screw all the time (instead of the metal job that earths out the low tension side when you push it), and a push button on the bars. It means having to make an insulated brush- and spring-holder for the cap - but it's a worthwhile mod.
Otherwise, the plastic-type end cap can be fitted - with the sprung strip inside against the cb screw and an earthing wire and button. That needs some new long screws and a holding clip fitting to keep it on. I've done that on one bike - for exactly LJ's reason - but though it's worked fine for ages, I'm not sure I like it all that much with a manual highly detachable cam ring: the alloy end cap does hold things together better.
Title: Re: auto/manual magneto
Post by: BSA_54A10 on 01.05. 2009 23:42
Yes you can but it is a recipe for a disaster.
We have a member with both fitted to the same maggy and you have no idea where you are.
I ridden it a couple of times and apart from allowing it to be retarded that far that you can start it with a fart it is a regular PIA when it comes to tuneing and offers no advantage riding because the bike will run very poorly if over advanced or over retarded.
The manual retarding mechanism simply bolts on to the end of the maggy in place of the standard end. The armatures are the same so every thing will line up.
OTOH the Rocket riders are always looking for the correct advance units ( a lot seem to have the B series ones fitted which turn the other way).
Title: Re: auto/manual magneto
Post by: coater87 on 02.05. 2009 00:34
 Thank you all,

 But my confusion on this mag stuff is never ending- I had no idea Lucas made so many different parts for the K2F mag- even looking at some pictures it looks like maybe the U.K. version may have been slightly different then the U.S. version? I ran into some old service sheets on the internet for Lucas, there were lots of "options".

 I think I will just relax on this one, keep an eye on E-Bay and hope I can find a nice auto advance unit (or better just the points housing without the "pipe"- the rest of mine is not broken).

 Maybe I will even look into a Joe Hunt for the everyday ride, and in the mean time get all the parts for a K2F together and off to a good re-builder.....

 The things I am finding most difficult to source are the little stuff, and it doesn't look like the proper nacelle and headlight bucket will be easy either.

 Oh, and just a while ago I found they got rid of the proper fork tubes, but I do have some nice ones that are 8 inches over-long if anyone really must have those! *lol* (I am just grateful they didnt have the money, or the welder to chop the neck!)

 Thanks again all,

Title: Re: auto/manual magneto
Post by: BSA_54A10 on 02.05. 2009 03:01
Go over to Daniel Bosses Super Rocket pages .
If you have the correct a series manual advance/retard some one there will happily swap you a standard one.
They did not make many of the A series one and a lot of owners end up with a B series one ( fits to the other side)
Title: Re: auto/manual magneto
Post by: groily on 02.05. 2009 06:33
Well, you definitely don't want manual and ATD A/R both functioning that's for sure! But there's nothing to stop a person locking the manual cam ring in place at the point of max advance, when the spark's at point of maximum flux on the armature, if the correct housing isn't to hand and an ATD is mounted. Or using the cable gubbins to do the anchoring - but not using it, of course.

The various mag model differences aren't that confusing when you get to look at the things close up Lee. There must be folk as 54A10 says who'd happily swap an end housing. The manual end housing with the cable control on the 'front' or 'left' looking at the cb end on the bike are best, in my view view, on anti-clockwise mags like ours unless there's a problem with room under the carburettor. Normal practice is to have the mag at full advance with the cable slack and the spring in the 'pipe' extended, so that if said cable breaks, the thing goes to full advance and stays there, or if the friction disappears at the lever as the screw backs off a tad, the cam ring can't gradually slip into retard mode. Having the other cable fixing requires the mag to be advanced by pulling the cable and compressing the spring - but works great for those machines with clockwise rotators.
All K2F armatures are the same (and the same as for the KVF for V twins). HT pick-ups are all interchangeable apart from on the K2FC model, slip rings and cam rings are different according to direction of rotation, cylinder configuration etc. Manual cam rings have a slot ground for the cable mechanism to hook up. End housings come in 3 basic types - plain for ATD use, AR cable on right, AR cable on left, and the mounting screws vary in location. Mag bodies aren't all drilled and tapped the same to take these - which is a nuisance when trying to make up a bitsa. And then there are the different end caps - the one with the tit in the picture above, the plastic type/types with kill button wire attached to spring strip, and the screw-on Competition type with carbon brush and spring. Pretty much all the bits are available, including ATD rebuilds (at a price that is hideous). Being too mean for that, I run my A with a rebuilt Competition mag (because I happened to have it available) with alloy timing pinion and cable A/R.