Machining Repairs

Machining Repairs

The most common method of holding a sprocket or gear on a magneto shaft is to use a taper. There are other methods which also work but it's not clear quite why a previous 'repairer' chose to use a cross drilled hole and a pin instead - and he had several attempts at getting it right.....
It was a straightforward weld and machine job to put this one right. 

The bearing on this Lucas MDBV had been pushed too hard against the rather fragile aluminium collar and it had cracked as a result. It didn't look as though it would last long and a gentle push confirmed just how weak it was.
We machined a recess in the mag body and made a steel plate, held in place with screws to effect a repair. 
A common problem! This time it's a Lucas K2F and we have plenty of those so we simply provided another body.
This Lucas MO1 had already been repaired when it arrived. A very nice engineering job but, unfortunately, whoever did it hadn't realised the importance of the bearing insulator - and left it out! Again, we were able to supply a replacement body.

This Saga S2 magneto had been badly damaged when the motorcycle it was fitted to was involved in a road accident. Where do you find another one?
The damaged aluminium was welded and re-machined.
The bent armature shaft was straightened as much as possible and then the taper re-machined to get it running true.
The missing points cap and clip as well as the pickups were all made from scratch.
 The end result was well worth the effort!

These pictures show, from left to right, an ML distributor cap with a very worn brush track, the same cap after it had been cleaned up and finally a BTH cap mounted in the lathe undergoing the same operation.

Some magnetos are held in place by a strap over the top of the magneto. If this strap comes loose, the magneto is free to move around which will inevitably fret away at both the base of the magneto and it's mounting platform. In bad cases it will be impossible to tighten up the strap without the magneto moving back to a position determined by the fretting process. This can make it very difficult to get correct chain tension or even to get the sprockets to stay in line. This is what had happened to the Maglita shown in the pictures below.
The picture on the left shows the fretted base as it arrived and the one on the right shows it after we had machined it flat again. Caution though - one, the same operation is almost certainly needed on the mounting platform and two, it is important to consider replacing the missing metal with shims to ensure that centre distance between the drive shafts is correct. Maybe not too important if it is chain drive but essential if the magneto is gear driven.

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