Magneto direction

Helpful information and requests for assitance and advice
Groily
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Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Magneto direction

Post by Groily »

You are.

R = clockwise from the DRIVE end, and L anti-clock from the DRIVE end - so it's as you say at cb side. Not all plates are marked though.
You can almost always re-notch, using a dremel or similar, to convert. Sometimes things get tight due to presence of other notches that you 'run into' but usually not.
Key thing is not to make a mistake in the position as that can cause problems!!
To help in not screwing up here, it is a very good idea to extract the eccentric limit-stop screw that is under a little pimple on the cb end housing. Find a standard 1/4BSF screw, and use it as a grub screw to lock the camplate into what you think is the best position for the opposite rotation. Then run the mag as fast as you can. The reason I say this is that you can often get excellent low speed sparks, but they disappear at high revs if the internal timing is over-advanced, because the magnetic flux 'bends' in the direction of rotation with speed. If the points open even a hint of a fraction before the 'right' moment, the spark will be lost. Better to be a tiny tad retarded internally than too advanced. Remember also that each thou extra on the points gap creates another degree or more of 'advance', and vice-versa as the gap is reduced.
Having got the advanced position right using a 12 thou gap, then grind the notch to give the required retard. About 10mm or 11mm wide is right for about 20-22° of movement, which is quite plenty. The eccenric pin, when refitted, gives you some adjustment for fine tuning.
Be just as careful with the AR cable notch. An error there, and the thing will drop out or pull out of engagement and that is a pain in the proverbial.

Note that camplates come in two or more thicknesses, and I don't know where you get new ones these days, hence preference for modifying. Too thin needs a spacer behind - fiddly - and too thick won't allow the circlip to fit . . . Wobble due to being too thin is bad as it can affect the points gap with the face cam - so things need to fit properly.

Good luck!
aobp11
Posts: 802
Joined: Wed Oct 12, 2005 10:45 pm
Location: GLD NETHERLANDS

Re: Magneto direction

Post by aobp11 »

You can almost always re-notch, using a dremel or similar, to convert.
Hello Bill, if L and R only differ in the position of the notches this would mean that the rising and falling edges at the same face plate are about equally steep, right?
Albert
Groily
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Posts: 2151
Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Magneto direction

Post by Groily »

Hi Albert,
It would, yes indeed. As with the on and off ramps on camrings, the on and off slopes on the plates seem to be the same and the points open just as 'snappily' going either way. (If they aren't, I haven't noticed any difference in performance after reversing rotation of the things, anyway!)
Theoretically, it should be quite easy to make these plates using CNC machinery. So it's a shame there aren't any new ones out there as far as I can see. Lucas camrings are available, for singles twins and Vs (and they work both ways subject to correct positioning ) but as far as I know, no-one offers camplates. Maybe there just isn't enough demand for them to be worth it - but I guard the few spares I have with considerable care! (The same goes for complete contact breaker assemblies of all sorts at the moment as well - new face cam ones are hens' teeth, and ringcam ones are also hard nowadays - even the steel ones which were plentiful. Neither type is fun to re-work when worn out or damaged, as lots of them are.)
Cheers, Bill
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