sr magneto refurb

[anthony kosecki]

My magneto hasn't been used in over 40 years and gives nothing resembling a half decent spark. New HT coils are available from Rex's speed shop but I don't know if this is the answer. Has anyone used these and how easy are they to replace? Basically, I don't have the skills or finesse for delicate/intricate work. Any advice would be most appreciated. Tony.

[Groily]

Replacing the coil on an SR is actually quite easy Tony. Not familar with the Rex speed shop winding, but typically there will be a live low tension wire attached to the coil, which goes to the little insulated nut and bolt on the side of the mag, and the earthing is done simply by virtue of its being sat on its cross-bar (armature) across the pole pieces. Where there is no low tension wire on a new coil, one would need soldering onto the side of the coil - but not too nadgery or delicate and needs very little finesse.
Suggest you test the resistance of the coil that is there with a meter - from the bobble or blade the HT lead touches to the central laminated bar, or any earth if assembled - you want to see several thousand ohms. About 6K would be pretty standard.
If Open Line or Infinite, then there's a break in the thing and a new one is indicated.

Removal requires undoing the 2 screws you'll see on the outside of the top of the mag going vertically downwards, and disconnecting the low tension live wire that goes to aforementioned fastener on the side. The screws - cross head or sometimes allen head - bear on the laminated armature to hold it in place and can be hard to undo owing to corrosion between steel and ali, but they will come. Penetrating oil is good. The coil can then be gently levered off its mount against the strength of the magnet and wiggled out of the casing.

Don't withdraw the rotor unless you have to (to play with the bearings), and don't withdraw the points cam from the spindle unless you absolutely have to, as it's a palaver to set it correctly (taper, but no keyway).

You should replace the condenser while you are there - plenty of options for that.

The Lucas instructions are pretty helpful on this, see for example the file here: http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf or the same thing in the Archives and many other places.

For any small parts needed, Dave Lindsley and others will be able to help - as indeed they would with rewinding your existing coil if need be.

Unless the rotor has lost its magnetism - which will be obvious as you turn it by hand if there is not a very noticeable 'flip' every half turn - SRs are not hard to deal with, and the cb side of it is no different really from a basic distributor.

[anthony kosecki]

Many thanks for the comprehensive explanation - and at 1 am! I feel less apprehensive about giving it a go. Didn't feel a 'kick' when turning by hand so that answers that question. Once again, thank you and have a happy christmas. Tony.

[Groily]

I get up early quite often - but not THAT early!!

If there is no discernible 'flip' when you turn the spindle, then it sounds as if the magnetism has gone AWOL over the past 40 years or so. Not totally surprising maybe! That will need handling by someone with the right kit, rotors being in some ways harder to do than fixed magnets owing to the curvature. You will need help on that, and ideally the thing needs 'keepering' once remagnetised and until it is back in, with the coil across the top. It's about the one thing one CAN'T do for oneself with these sadly. But good luck - and merry crimble to you too!
Cheers, Bill

[Rob Harknett]

I assume you did what you usually need to do, perhaps after just one winter lay up. Clean and set points gap, clean coil contact solder blob, clean cap contact tab. Remake lead contact tab an grub screw. Remake contact in lead to plug cap, use a new plug. If that fails try a new condenser before you do a rebuild.

[anthony kosecki]

Rob, Thanks for the additional advice. I cleaned what I could and changed the easy to get to capacitor but no joy. I've read more on the website (excellent articles btw) and have come to the conclusion that it's a case of getting in touch with Kettering. Thanks for the advice from you both and here's wishing you a happy christmas. Tony