The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Triton Thrasher on 09.03. 2009 12:11
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Because of onset of banging and missing, I seem to be having to clean regularly, the slip ring on my K2F Magneto. There's no oil on it, but it leaves a black mark on a rag. The odd thing is, I'd heard scare stories about soft HT brushes so when I found that the new ones I bought left more of a mark on paper than the old ones did, I put the old brushes back in. They were not much shorter than the new ones.
Should I coat the slip ring with WD40 or leave it dry?
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TT: Where did you get the pickups from? I got a pair from EBay and they were absolutely fine and did not mark paper. They weren't that expensive either. When I installed them I cleaned the slip ring with brake cleaner and had no further problems. The original ones were fine for ages but suddenly seemed to "go soft" for reasons I never fathomed.
I can look back in my EBay history and find where i got mine if it helps.
Cheers
Z
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Thanks ZM- People tell me Tony Cooper sells good ones, but it's the old fashioned cheque with order payment, which slows things down. Your Ebay contact would be interesting.
Interesting that old ones can "go funny."
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Black residue is evidence of foreign substance, most likely condensed oil vapor from the timing chest getting by the shaft seal and causing poor contact which is why you have "banging and missing". Replace the seal, clean up the shaft and you should be fine.
David
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Independant ignition sell brushes which they say are better due to being 'softer'(how softer I don't know) because the ones I had in before were too hard and had scored the slip ring allowing the spark to track all the way round causing all sorts of issues.I only buy my brushes from them now without any issues since.
Andy
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TT: Yep Tony Cooper certainly does sell good ones (He's the chap who did the dynamo for the Dommie and the Magneto for the A7). The EBayer I got them from was Classic Solutions (EBay ID: classicsolutionsuk) but I have a feeling they are no longer trading as their web site is now just a collection of bike images and they have nothing for sale on EBay. When my mate needed a couple of pickups he told Tony he needed them urgently and he sent them before he received the payment.
Cheers
Z
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To answer your question, TT, I think it would be detrimental to put any sort of lubricant on the slip ring. The slip ring should be as clean and smooth as possible with no contaminants. Any hydrocarbon you put in there will make the brushes ride on an oil film and arc when the plugs fire, putting carbon on the slip ring and burning it. Have you checked your ground brush? It's usually the one that gets really oily when the seal fails and then just burns a pit into the commutator.
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I'd say 'No' to anything slimy on the slip ring, and 'yes' to dp's 'get a new oil seal' thought.
All old mags seem to have a pit on the brass bit where the earth brush runs (it's nearer the slime as beezalex says). Reconditioners turn the brass down to get a good surface - provided doing so doesn't cut too close to the steel pins that hold the brass end in place against the coil. That can be quite a few thou off the diameter sometimes.
I'd replace the drive-end seal, bearings and insulators, all brushes and springs, check slip ring for no ridges and tracking and then know there were no mechanical faults. I might also replace the points and/or backplate. If it still didn't work correctly, I'd either put a new condenser in, which is a lot of work relatively, or get a rewound exchange armature which addresses the 2 questions which are hard to answer - is the condenser dead or are the windings breaking down? Or both? I swear by magnetos and would never be without one where there's a choice - but they do have to be in decent shape.
As to Classic Solutions . . .???? Seem to have gone awol as zitman said. But Tony Cooper, Sean Hawker and SRM can help, as can Dave Lindsley. Shouldn't be a problem to solve whatever aileth.
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I had an idea you guys would know a thing or two about magnetos. Ta.
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Confession time! My slip ring tracking problem seems to have been caused by an HT brush being displaced and running sideways on the ring. The rear pickup is awkward to remove and replace on this ?well known Brit twin,? so I had not taken it out to check, since putting it in wrongly.
Found it last night but then found the bike still ran terribly and sooted up the timing side plug. I gave up, but then went back out at half past ten to fit new needle jets. Or rather to fit one needle jet, as I seem to have bought one .106 and one .105 jet. That?s when I found the jet holder was half-unscrewed in the timing side Concentric.
There?s room for improvement in workmanship in this shed!
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what's that old saying "If you think it's sparks it's the Carb and if you think it's the carb it's sparks"
All the best - Bill
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Yes, or if you think it's either it's both.
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And it you think it's both, it's neither. Then it's compression.
Lannis