K2F magneto bearing

[geechr]

I have just been retiming my G11 and I noticed, after loosening the magneto gear, that there was at least 2mm side to side movement of the magneto shaft. I assume that this means that the bearing/s need replacing but just before I take the magneto out I thought I would check with the experts on this forum.

Regards

Chris Gee

[itma]

It can be done, with care.
better advice will be forthcoming no doubt

[wilko]

The tricky part is getting the insulators into place with the new bearings and also removing the outer races,you will need a special puller for the inner races as well. Sometimes (if the bearings still feel smooth ) you can remove the shims behind the points end housing to remove play.Best you get an expert, but then he'll convince you to do the whole thing! Dugless

[Don Madden]

The best advice I can offer is to heed that of Ken. Magnetos are a bit tricky to do & if yours has not been rebuilt by a specialist since manufacture, it will need attention by one now.

They can be serviced if in good condition with care by following detailed instructions. Do not attempt to strip it without them or you will do more damage than good.

If the drive end is loose, the insulcups & seals will need replacing. The bearings may be servicable but only inspection will determine. Outer races are easy to remove but inners are difficult. I use special made pullers for them.

Cheers, Don.

[geechr]

Thanks for all the helpful advice.

I've just removed the magneto from the bike and to my astonishment I found that there was no insulator around the drive end bearing and the one around the points end was partly missing. The outer races just fell out. I wonder whether this is the cause of the poor running of the bike?

I have yet to determine whether the bearing housings have been worn or, when the insulators are replaced, the outer races will be held tight.

Chris Gee

[GSAX1]

The insulators are available in one oversize. Beware, they are very difficult to fit.

Michael

[Groily]

Almost certainly the cause of the bad running. The insulators insulate . . . if they're in tatters or AWOL they don't - bad - . . . plus you get the slack on the shaft - 2mm you say - which will certainly give very dubious points gaps and very hit-and-miss timing between cylinders. If the bearings show no tracking or marking and there's no other obvious damage, I'd simply fit new insulators to start with as the bearings are expensive. The housings will bear witness to rotating outer races if that's been the case .. . I'm not sure why insulators are reckoned to be so hard to fit, maybe I've forgotten something, but it should all go together easily enough. If the outers are snug with the new insulators in there you should be OK on that part. Then, with or without shims between the end housing and the mag body, you should be able to set the thing up with smooth rotation but minimal end float, and points gap close to the same (ie within a couple of thou) on both cylinders, and away you go. Shims are available in various thicknesses from, I think, 2 thou up to about 10 or more - Independent Ignition Supplies list them. If there is still up-and-down movement on the armature shaft or it rotates less than smoothly, you'll need to replace the bearings. But your being by now an expert, that's no prob - subject to getting the inner races off. One old trick for that is to wrap thickish copper wire in their tracks (must be proud of the race itself), clamp the race in soft-jaws in a vice by the wire tourniquet, and then tap firmly on the armature with a non-ferrous whacking implement. Usually works - but when it doesn't, an extractor is the only safe answer, and, as far as I know, not an obtainable service tool . . . ergo it's make or borrow. If there is a tool commercially available out there, I'd like one too!
Worth adding that lots of people think they need a new cam ring when the points gap is uneven between cylinders. They are often wrong - the end-housing or the bearing are far more often the culprit.