Lucas K2F Magneto with oily earthing brush

[shaunstaples]

Thought I had read a post about this, but cant find anything now.

Getting nearer to a test ride, but its cutting out anything near 1/2 throttle. The Carb jetting and slide cutaway was wrong, so as a start I've acquired another carb and correct slide and jets. Still cutting out, seems worse if anything.
Had a look at brushes for HT leads and they look ok, but the earthing brush has come out like a dipstick!
I read there are 2 different size seals for drive end, pre 55 and post 55 but cant find any listed on club spares site?
The timing seemed too far advanced as it kicked back, even with lever fully retarded, so I did a quick check yesterday afternoon and points were opening just over 1/2" btdc, so waiting for a puller to get the gear off.

Am I right in thinking it will be the oil seal or could it be too much of the wrong type grease on the drive end bearing?
Also will I be able to replace the oil seal without any other special tools?

I managed to get a pic of the earth slip ring ( not very good but can see how reflective / oily)

[Groily]

Couple of things Shaun. Oil inside may cause spark trouble but not always. Oil all over the points at the other end definitely will though. Oil entry is commonly via a tired seal - but also quite often down the HT leads if the engine has been a bit leaky.
Mags come with 15mm and 18mm shafts at the drive end. Most post '52 ones are 18mm. The seals for both can be had but fitting requires extraction of the drive end bearing outer race and a new insulator cup between it and the housing. The insulators come in 2 thicknesses (at least). Sometimes bearing races literally fall out - if you are lucky. Other times they are tricky to get out. On reassembly, with the mag body warmed (dunk that end in, eg, boiling water for a few) the race and new insulator should be a tight fit so the bearing won't fret. More than 'push hard with your fingers fit', less than a tight press fit which would rip the insulator. A light series of taps using a suitable mandrel in the race, with insulator lightly glued on rear of race, works nicely.
Then you will usually need to check endfloat of assembled mag. Ideally, zero at room temp, or a thou or two. Not negative, and not sloppy. Shims can be added,and subtracted on the armature behind either bearing inner race (they can also be swines to extract) or in case of negative float by shims between main body and cb end housing.
If slipring has any damage, replacement is the only option. If the track the earth brush runs on has 'dimples', they ideally need removing by light turning in a lathe. In rare cases the dimples are so deep they cause other difficulties, but let's not go there unless really necessary!

[shaunstaples]

Thanks Bill (Again), When you rev it up it starts to cut out / misfire, so initially thought of carb as only the bent needle and needle jet were right, along with 1/4 of a manifold gasket missing and badly pulled flange was loose with both the bolts stripped! I was hoping after finding that lot, I would be getting a test ride, sadly not!

Bit more revving, seems to be related to engine speed rather than throttle position, as if the oil is lifting brush off track or something?
The points end is dry although arcing a lot but this doesn't really alter when it misfires.
The HT leads are very short and LH one has a tight bend under carb, so going to replace and try and re-route them.

Thank you for the insight into getting to the seal, its not put me off! and going to fetch puller this morning...

[Groily]

Bit more revving, seems to be related to engine speed rather than throttle position, as if the oil is lifting brush off track or something?
The points end is dry although arcing a lot but this doesn't really alter when it misfires.

Thank you for the insight into getting to the seal, its not put me off! and going to fetch puller this morning...

Hmm . . . the constant arcing at the points suggests condenser failure as #1 (classic) possibility / probability.
The points may well be quite pitted if you hoick them off and have a good look - that goes with the arcing.
If you want to have a look at some good and bad sparking at points to get a feel for how yours compares, the link here will show you some fireworks, and some of what you should see - ie small pinpricks, no big yellow flashes, etc. An original condenser will have deteriorated for sure, and a replacement may possibly also be playing up, much depends on what it is exactly, how old and maybe even how the bike's been stored.

http://www.brightsparkmagnetos.com/gall ... arcing.htm

To get the bearing race out if it's stuck is not something for a straightforward puller unfortunately - you have to get into 'no space at all' with something that will encourage the race to start to shift, usually with a bit of heat-gun type heat to help (or boiling water blah blah). Excess heat is one of the enemies of magnets, so try not to get the whole thing too darn hot! The pic here shows what I use, a 'camming action' using a nut on a threaded rod which forces sharp bits into the 'space' where the insulator is and gets the race started (99% of the time anyway!) The 'sharp bits' are countersunk screw heads, the harder the better. Commercial tools are probably available though - but not sure 'from whom & how much'!

http://www.brightsparkmagnetos.com/work ... /index.htm

More Good Luck!
Bill

[shaunstaples]

Puller was only to get gear off, would have to make something to get outer race out.



Have seen them easy cap condensers and was thinking of going down that route. looks like they go in place of the insulator under the points.
Don't think I'm going fast enough for Catherine Wheel but guessing way below 100nF

https://youtube.com/shorts/tPt6qNdDWGE?feature=share

[Groily]

That's a lot of arcing Shaun, not so far off 'no capacitor' in the examples. Note that those examples were all done using a K1F off a Velocette, not a twin, so only one lot of fireworks per rev. Quite enough pyrotechnics, mind!
Should just be the pinpricks as shown in the 150nF / 220nF zones and you are a million miles off that.

The points will need a bit of attention almost for sure - but will usually come up to 'ok', which is just as well as they are rocking horse droppings at the moment. Check the pivot of the opening point for slop - 'tis a common cause of a) 'bounce' and b) an incorrect firing interval between cylinders. Nadgery to make and replace because they are a fiddly stepped design and are peened / riveted on the rear of the backplate, but worth the effort, and you can make the diameter of the post a fraction larger so you can true up the ovalised hole in the fibre bit.

Nice solid pinion puller! So there's a good start . ..

Not for me to suggest what you should fit as I'm not a pernicious vendor, but you do need to replace the capacitor almost for certain. You should also check out HT coil and slipring if you can because you don't want to do a lot of work and still have trouble. (EasyCaps are reasonably easy to fit on K2Fs and similar because you don't HAVE to strip the armature to its elements, but if there is other work to be done, there are lots of choices.) Not replacing an old slipring is a false economy almost always, while these things are apart.

Original coils WILL be tired, but may sometimes be 'OK for now'. They need to be continuous (- about 5000 ohms on your meter between brass on slipring that the HT brushes run on, to the spindle. Open Line or Infinity Ohms = a break the spark is having to jump inside the coil or that the slipring isn't cleanly attached. Neither is good news.) And the coil itself needs to be solid or very firm to the squeeze, when hot. Ie about 50-60°C. If it's squidgy and deforms as you squeeze, the insulation is breaking down. If it melts and oozes out, the resulting glue can seize the mag solid, and cause other damage - DAMHIK!

[shaunstaples]

Yes I was surprised how much arcing there is, but should be able to sort that with an Easy Cap condenser.
The points definitely need a fettle as they've had a battering.
Armed with this info should be able to get it back up to scratch, if it doesn't need a rewind.

I can't take credit for the puller, that's my long suffering (from my requests) friend Glyn (Norton, Sunbeam and Enfield Pedigree) 50 yrs in precision engineering

Again plenty of quality info that's easy to digest
Thank you

[shaunstaples]

Finally got back in garage yesterday and stripped the magneto for a look.
The thick oil/grease was all over earth slip ring, but I don't think it was from the timing case I just think there was way too much on the front bearing? The seal looks new and is soft and seems tight on the taper when bearing is running in race. Also there's a trace mark on taper where seal has been running.( forgot to take picture before cleaning!)

Earth slip ring.jpeg

Grease.jpeg

The LT coil measured 0.55 ohm
The HT coil measured 4.85k
I've only got my Trusty Aldi meter working, so checking condenser is a bit hit and miss, it does rise a little as though its charging but doesn't seem much, like its almost open circuit ( if I'm doing it right?)
The windings are hard definitely not squidgy, but haven't warmed them.
Slip rings have cleaned up lovely, as have the points ( looked worse than they were )
It all looks like a recent-ish overhaul?

Earth Slip ring connection.jpeg

Earth Slip ring connections.jpeg

So put everything back together and retried it, still cutting out and misfiring when revs increase! Spark still performing well too!

Ordered an EasyCap condenser tonight, so will try isolating existing condenser when that comes.

My Friend has loaned me a magneto from an Enfield twin which is clockwise. Would it be as simple as swapping points assembly just to try and prove it?

RH mag.jpeg

[Groily]

Definitely a decent not-so-long ago rebuild Shaun.

Coil in all probability is quite fine. Readings are good. There's a modern condenser in there already but can't quite see what sort. To measure capacitance and 'leak-proofness' it has to be disconnected from the coil to get the windings 'out of the equation', and a meter that measures capacitance is required. (Disconnected, if you put a meter on the high resistance scale across it, the resistance should rise extremely rapidly to 'infinite' as the meter's little battery tries to charge the capacitor and naturally enough, fails! But that's a very basic test and only a part of the story. If you had an insulation tester or 'megga' . . . then with pulses of 250v minimum you'd want it to rise to the limit of the tester, usually about 2 giga-ohms.)

Given that the low tension wires are accessible - the live side is the one on the opposite side, opposite end, to the plastic 'nose' where the coil goes into the slipring - that could be snipped and insulated with a bit of heat-shrink to disable it for fitting an EasyCap if you wanted, without having to dismantle the armature. The other, earth side for condenser and coil, would remain undisturbed.

Does look as if there was rather a lot of grease in there. If the seal remains flexible and not perished or cracked, then could be it's fine too.

The armature thread has lost a turn or two over the years, but five turns of threads are enough. There should I think be seven.
The taper is tired, but hopefully reasonably OK all round where the seal sits - there's not a whole lot you can easily do about that.

Glad the points cleaned up. The bearings are probably good too. As long as the tracks for the balls aren't black, pitted, rusty (no chance!) or otherwise damaged and it all turns nicely, I don't think there's a lot to worry about there. See previous comments for end float which is quite important - and is, again, probably OK if set up right last time round.

The brass end-cheek the earth brush runs on has been cleaned up in the past and looks OK - you can see the ridge adjacent the coil which shows original diameter compared to cleaned-up dia (turned down to remove dimples caused by the return current at each firing point of the mag). You could give it a good rub to make it shiny again and a bit smoother if you wanted.

If it were me, which of course it isn't, I'd just snip the live side and fit that Easycap on the points and run it up again to see. Low cost and low hassle factor, and should probably fix the arcing.

And NO, you can't use those clockwise bits I'm afraid. The points are handed and the clockwise ones won't open at the right spot on the camring by a country mile. Plus the fact that, mechanically, the heel that opens them needs to 'trail' not lead . . .

[shaunstaples]

I thought the thread was a bit short only because there is about 3/4 of the nut doing anything, and had spotted the undercut on brass ring.
Hadn't thought about cone on slipring, was going to unsolder the one I thought it was and check resistance.
Everything looks good and has cleaned up lovely. The end float feels right, it's not tight and there's no detectable play when screwed up.

Just wanted to test after getting it cleaned up, otherwise wouldn't know what fixed it.

Will the soldered wire to earth in pic be return side of condenser and winding connection buried in resin?
EasyCap should come mid week.

I thought not, and I'm not going to disturb either of the mags bearings swapping anything else.
If It was an anticlockwise mag I would be able to prove its the Mag but not what's wrong with the Mag...Just got to be Patient.

Found my old trials bike stuff, the points cam on my TY250 was like a wedge and you couldn't adjust the timing on a sliding plate, it was adjusted by the point of break of the points and no points gap setting, (46 year memory card being played here) So my Dad (RIP) made me an adapter for a clock gauge. This made such a difference to slow running performance.
Had to make a longer rod, and would rather have it straight on top of piston, but will give it a try.

Clock Gauge Adapter.jpeg