Grooved Mag Slip Ring

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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The-Pope
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Joined: Fri Jun 03, 2022 9:35 pm
Location: Uk

Grooved Mag Slip Ring

Post by The-Pope »

So I believe I have found out why it is off a cylinder. The offside pot pick up looked to be out of place. Brush looked quite beaten. Put it back in on road side. Still wouldn’t start. Looked again brush snapped. I though I could feel a step/groove with the dowel when cleaning slip ring but didn’t want to try with fingers! Trying to do it on a budget and the budget wont stretch to a mag rebuild so have gone for a Thorspark after reading good things on here. Would rather have reliability over originality in this case. Just need to get it charging then so the battery can stay charged. Any advice or tips on fitting the Thorspark would be great. Thanks.
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dave16mct
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Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: Grooved Mag Slip Ring

Post by dave16mct »

Just check that the Thorspark unit won't earth out on the mag spindle or the back of the points housing (and have a load of spare fuses in the toolbox). Some K2F mags have a thicker spindle and may touch the bore of the Thorspark. They may do 2 bore sizes, not sure?? Groilly will be along to say which years of K2F have the different spindle size? Mine kept shorting out and blowing the tiny fuse, I gave up and fitted Boyer bransden - perfect now. I'm going to build the Thorspark into another mag with thinner spindle.....one day.
Dave.
Groily
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Joined: Thu Jul 04, 2002 1:00 am
Location: NORMANDIE FRANCE

Re: Grooved Mag Slip Ring

Post by Groily »

Ref the spindles . . .
While early K2Fs had 15mm bearings on the drive end, rather than the 18mm fitted from around 1952, the cb ends are the same and the difference the other end should make no odds to fitting the Thorspark bits at the contact breaker end.

That isn't to say that cb end spindle dia is guaranteed identical to half a thou on all and every, but they'll be close and should all be the same because they all take a 15mm id bearing outboard the slipring, which has to go on snugly.
A lack of clearance between the Thorspark parts and the spindle could perhaps be caused by non-concentricity of the housing on the mag body, often caused by a poorly-fitted or damaged bearing insulator inside. Or even, dare one say, by a variation in the finished bore of the Thorspark plate?
g5wqian
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Location: wiltshire
Location: near swindon wilts

Re: Grooved Mag Slip Ring

Post by g5wqian »

i have a model 30 ajs and my dad had one new in the 1950s , he told me they had issues in the 50s with the slip ring brass wearing away and then the engine misfiring etc .
The-Pope
Posts: 14
Joined: Fri Jun 03, 2022 9:35 pm
Location: Uk

Re: Grooved Mag Slip Ring

Post by The-Pope »

Thanks for the information ref the spindles. Fingers crossed it will work ok. I have looked in the mag with an endoscope and the groove is huge with a step onto the brass and it looks like some of the surface has pitted/broken away. Amazed it ran at all (Idont have a way to host photos so can’t get them on here). It’s a shame as it it started first kick and ran well for the 6 miles to the fuel station (first time on the road for over 50years I believe). Let’s hope the Thorspark lives up to other experiences I have read about. Meanwhile….. let’s see why it’s not charging!
Thanks again.
g5wqian
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Joined: Wed Nov 18, 2015 7:43 am
Location: wiltshire
Location: near swindon wilts

Re: Grooved Mag Slip Ring

Post by g5wqian »

if its not charging look what voltage regulator you have , if its the old lucas mcr2 then get a DVR2 solid state regulator and put that in .
check the fuse first though and for broken wires near the battery , or for battery wires trapped and rubbing the frame and shorted out .
check the voltage when engine stopped and running just to make sure it isnt just the ammeter at fault .

oil can get into the dynamo and mess things up , you can give the internals a clean out using a can of brake cleaner and giving it a good spray out and then blow out with compressed air and let dry for a while , its also easy enough to remove dynamo and wash it out with brake cleaner and put back in again , i use the clubs gasket/seal for the back of dynamo to timing case and put welseal on it and when all fixed in place leave it overnight for the sealant to cure off .

new dynamo brushes may take a minute or so of engine running before they bed in and make contact and the dynamo kicks in but also the engine needs to be above about 1100rpm before it will excite the dynamo into charging .
The-Pope
Posts: 14
Joined: Fri Jun 03, 2022 9:35 pm
Location: Uk

Re: Grooved Mag Slip Ring

Post by The-Pope »

Thanks I’ll go through this and see what’s what. Would not surprise me if voltage reg is the issue. Looks very tired and like it’s been hot! Cheers.
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