The problem is ignition related. If the bike is left unused for a few days (yes, I know it shouldn't but I'm sick of repairing salt damage and I've also just moved house) there is no (as tonight) or very little spark and the old dear will not start. Clean the points - which aren't dirty - and the various brushes/slip rings and voila!! A big bright fat blue spark and she starts easily and idles like a dumper truck. It is usually sufficient to polish the points (new) with fine emery. Have you ever heard of points oxidising like that? - Will Noble 10/4/2001?
If a magneto seems to suffer from self-dirtying points, (which classically is a duff condenser but you would see the excessive sparking if you removed the cap when running) this could of course be due to a worn out oil seal around its drive shaft letting oil vapour breathe into the magneto and coat it, but in my case I think it was the deteriorating shellac of the armature windings releasing an emulsion/vapour of some type. This coated the surfaces you mention. It was an original 1961 mag, left to stand in a lockup garage for over 10 years. It surprisingly worked after the points and pickup were cleaned and though very tired ran adequately for a while until it seized solid when the melted shellac solidified at the mid-point of a lengthy hot run (i.e. 100 miles from home, naturally - but I tapped out and cleaned up the armature and made it home without stopping the engine and with a cup full of petrol to spare, then removed the armature before it set again.) I think it might be wise to have your mag serviced.... but someone may know a scientific reason. - TW
Reference the mag:
It is already a rewound item (FTW Motorcycles) with new condenser/slipring/bearings etc. The only thing that was not replaced was the oil-seal on the drive end and I have a new one available so here goes......... although it doesn't seem to show evidence of oil entering the mag. Incidentally, do you know of a source of platinum points?? It's a Lucas K1F. - WN
I doubt it is the seal unless it looks suspect - they seem to go on for ever.
If FTW thought it serviceable I'm sure it is, and we'd need to think about
whether your engine is a "heavy breather", it needs both that and a
worn/damaged seal to cause a problem.
Are you smoky, heavy oil consumption etc?
I'd hold off doing anything until some long hot runs had settled everything down and dried everything out.... - TW
Yes, it is a heavy breather - even with the later Velo mod breather in the back of the timing chest. Yes, it is a smoky old beggar and consequently uses a fair bit of oil - not much dropped, some burnt and a fair amount thrown into the primary and out of every connected orifice onto the chain/wheel/tyre/wife/top box etc. (Only benefit - chain doesn't wear much and back end (and wife's) doesn't rust! Having read all the correspondence in Fishtail recently about big-end oil feed quills possibly causing over-oiling of the top end, I have just modified the feed quill by increasing the cross-drilling size to 1/8" from the previous (5/64"ish if I remember correctly). It is a home made solid stainless steel version produced to same dimensions as "original" brass version which kept on breaking the parallel quill off, from I suspect crank flex battering it about - the old dear is well thrashed. That said, I have not done much running since the mod - at the weekend - to determine if it has helped the smoky bit. I don't suppose anyone will ever come up with an explanation as to why some engines breathe oil everywhere and some never blow out a drop. My local partner in Velo associated lunacy, Boyd Stokes, has a Venom Clubman which is ridden hard and never burns or looses a drop (see Fishtails 288/289) and I remember seeing Adrian Bolge's MAC a few years ago which didn't even have an inspection cap on the primary but the outside had no oil splattered about - every other kind of gunge was evident though!! - WN
A couple of developments ref IM001 - my ignition problem with the MAC.
1st, I have proved it is the earth slip ring/brush that is the problem area. Clean it (of oil) and away she goes - usually first kick!!
......so oil IS getting into the mag (through the oilseal on the drive end, I assume.)
To try to combat this without tearing it apart, I've had a look at the breathing arrangements, surmising that the engine is pressurising the crankcase - hence oil in mag, all over the back end etc. etc.. As stated before, the later Velo mod breather is fitted in the back of the timing chest, but over the years I had got so fed up with it blowing oil out of the tank breather - despite all pipes being the correct length- that I had clamped the pipe shut before it got to the oil tank - so I released the pipe clamp. Oil blowing out of the tank breather again! Blast! Flash of inspiration.... Only part open the clamp, you clot. Magic! Very little oil blowing anywhere, even out of the primary drive. In fact it was even remarked at the recent Loch Ness Rally that I was showing up the three other Velos by NOT having drips underneath the bike. Now that IS a first!!
The old girl still oils the slip ring but takes hundreds of miles now instead of tens. Guess it's off with the mag and in with that seal.
2nd, the only negative report is that she definitely burns oil - proved because it's no longer on the floor/back end. Even Cord rings don't cure everything! - Will Noble 15/6/2001