The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Minto on 20.05. 2021 15:54
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Hey wise and enlightened ones
I'm concerned that the spring part of the points on my K2f is making contact with the cam ring, is this normal?
Thanks
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It does run close to the camring
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Shouldn't kiss the ring, no. If it does, it shorts out the low tension side because the opening point and spring are live.
If you take the cb assy off and loosen the small screw at the 'far end' of the blade, it's slotted to give adjustment. Tighten the arc, and you should get a clearance. Don't need a massive amount, but has to be a bit. Might, worst case, have to elongate the slot a fraction, some of the pattern parts aren't perfect.
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Shouldn't kiss the ring, no. If it does, it shorts out the low tension side because the opening point and spring are live.
If you take the cb assy off and loosen the small screw at the 'far end' of the blade, it's slotted to give adjustment. Tighten the arc, and you should get a clearance. Don't need a massive amount, but has to be a bit. Might, worst case, have to elongate the slot a fraction, some of the pattern parts aren't perfect.
Thanks for that, I thought it was wrong. I'll have to elongate that slot a smidge, the screw's already at the end.
Cheers
Jase
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Happens too often Jase I'm afraid.
The geometry of the opening point pivot (the 'ole in the fibre bit) might be a fraction off, or the blade not made quite right slot-wise, or even the backplate, if a pattern one, might have the pivot post a few thou out of position. It's all it takes.
I believe Grove Classics, the Velo people, are now making the bits for the steel units having acquired the tooling and the rights, but haven't seen anything specific on their web site so far. If true, then we might expect some tighter QC - maybe!
If in your travels you come across a decent brass type, of the earlier generation, I'd grab it.
They are in many people's view 'better' for four reasons:
first, the opening point and spring are the LT earth side so a kiss doesn't kill the spark;
secondly, the double spring blade of the brass types is gentler in operation than the steel equivalent;
thirdly the points gap stays in adjustment longer (as a rule) for not relying on friction on sliding bits.
Fourthly, quite often, the contacts mate a lot more squarely too.
And a fifth plus point is that you get the option of an auxiliary earth brush on the back face, which can help reduce the dimpling at the firing points of the mag that is caused on the armature drive end brass piece by return current through the main earth brush.
If only someone could be encouraged to make new brass types (and the points too), it would save a load of trouble. 2nd-hand ones are OK if you get a good one where the pivot post isn't worn right down (and the points don't wobble) - but it's a fiddle to repair them.
It's also worth knowing that if you come across a decent BTH anti-clockwise backplate off, say, a KC2, that'll work very nicely too. Main dimensions are the same, the integral keyway that sets the internal timing is in the same place and the design is better too. New complete BTH assemblies can be had - but you need a mortgage. A Bosch set will also serve and is well made - but the keyway will probably need suppressing and reforming in the right place, or the camring repositioning.
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Thanks for the advice Bill and Bill, first port of call for me is trying to file a few mm extra slot in that spring to see if I can move it away from the cam ring.
Or I might just replace with a new set.
Last year I had the kill switch earth brush disintegrate, I kept finding bits of it in the CB end for weeks, every time it started misfiring I'd open it up and find a bit more. I thought I'd got it all but found another few lumps of it today. I suppose if there's bits of that being flung around in there, it wouldn't take much caught between the ring and spring to cause problems. It has now all been cleaned out.. I think!
Jase
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Spring filed, now got a good 2mm clearance.
Jase
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Result! Not TOO high a tension on it hopefully, but anyway that's a problem sussed.
Polish up the head of the centre screw to give the new earth brush an easy ride, and with any luck things will hang together . . .
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The GF refused to start last weekend so I pulled the plugs and there was bugger all spark. After checking the blindingly obvious I remembered this thread and checked whether the points spring was touching the cam. It was, so I pulled the points off and adjusted the spring - Result!
Being able to use the wisdom and experience of everyone on this forum has saved me so much effort and wasted time it's worth my computers weight in gold!
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Nice one, I'm hoping it might've sorted a misfire I had before I stripped the engine (not the reason for stripping it). Hopefully find out before the weekend
Jase