Author Topic: Points gap question  (Read 673 times)

Online groily

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Re: Points gap question
« Reply #15 on: 09.12. 2018 07:03 »
Several things Uncle D.
First, the centre screw is correct for the brass type.
Second, on any anti-clockwise drive K2F the upper cam lobe fires the pick-up next to the engine, the lower one fires the one the gearbox side. Which goes to L and R plug is up to you when you time the ignition.
Third, I also don't think those teeth are meshing deeply enough, but could just be the pic. If in doubt, hold off running things until doubt dispelled, as the teeth have a habit of stripping.
Fourth, the variation in gap is too big.

Rather than join Berger at the pub (it's shut now anyway!), you could try loosening the screws that hold the camring housing on. Wiggle it a bit and retighten. You might be surprised.
If OTOH that does nothing useful, you could take the screws out again and take the whole housing off to see whether the race for the bearing looks central and that there is a decent insulator washer behind it. Poor seating is a common reason for error. If the outer race comes or falls out of the housing easily, that is bad. They should be buggers to extract, needing gentle heat and a careful line of attack.
(Am assuming there is no up and down or axial wobble on the armature due to wear or poor assembly, with everything screwed up tight. Also that the camring isn't loose.)

You could also fit a different set of points if you had one handy, to see if the problem persists.

The cb will come off in the end - wiggle and wiggle some more with the centre screw, the needle-nosed pliers or whatever..

(Generally speaking, any wobble in rotation of the cb unit on the armature will affect both sides the same. You could waste a lot of time trying to make it turn as true as you like, without solving the gap variation problem. Getting the firing interval between sparks correct on a K2F is one of the hardest jobs.)

Bill

Offline Swarfcut

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Re: Points gap question
« Reply #16 on: 09.12. 2018 08:32 »
 Bill.. Well said.  A good few tricks to try there.  Sometimes the search for true perfection is just not worth it. Chasing the last 5% will be the aspect that swallows the bulk of the cash, so I would assemble carefully with what is to hand and have a basic runner. Chances are a better maggy will come along at some stage.

  UncleD... Keep on spannering, almost there now.

   Swarfy.

Offline UncleD

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Re: Points gap question
« Reply #17 on: 09.12. 2018 10:30 »
Thanks to both of you.  I am a person who drives for perfection but also makes rational decisions.

One of my benchmarks is that I don't leave the shed & tools 'in process' and don't like to leave bikes open/ half done.  So, with no pathway forward I reassembled the mag and put the timing cover back on (albeit without sealant on the gasket so it will come off easily) and gave the bike a kick.  She started second time so I took her for a run to see if I could find Berger and send him home.  She ran beautifully, unbalanced points gap and all.

Whatever it is both pisses me off and is not a burning priority...don't you love the world of the in between?

Groily, I will think about and pursue all that you have suggested because if I have one priority it is to learn as much about this bike (and my A65T) as possible. The next best thing to riding is learning.

On a Sunday night however, with two running Beesa's in the shed, the rain bucketing down and a cool 29 degrees, I am sipping on my single malt feeling very satisfied.

Be prepared for a barrage of questions next weekend!

Northern Territory, Australia

Online JulianS

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Re: Points gap question
« Reply #18 on: 09.12. 2018 10:40 »
If you get inside the mag you may find that the bearing insulator at either end is damaged. They are either flimsy paper or stonger plasticised material, but inserting them into the case or points end cover with the bearing outer sometimes either displaces them or damages the petals, causing the bearing to sit off centre and gining you a variation in points gap.

Offline UncleD

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Re: Points gap question
« Reply #19 on: 09.12. 2018 12:04 »
I have to say that I am reluctant to dismantle beyond the points both because this is very new to me but also because the bike seems to run OK at present.

If she would not start or was runnng poorly, I'd jump in but at the moment it seems a risk.

I'm not sure if you are following my post in the Engine section but theer has been some question as to whether the mag gear is meshing sufficiently with the drive? cog.  The tips of the mag gears do connect but not deeply.

Could this be related at all?

Northern Territory, Australia

Online JulianS

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Re: Points gap question
« Reply #20 on: 09.12. 2018 13:21 »
Mags run with all sorts of issues.

One last suggestion - just remove the points assembly and check that the key on reverse does not protrude too far causing the assembly to seat at an angle, check the taper on it and the one in the armature at the same time.

Online groily

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Re: Points gap question
« Reply #21 on: 09.12. 2018 14:35 »
Don't think necessarily related Uncle D - but having blown the pic up to see the lack of tooth engagement  . . . I'd worry a bit and I'd rotate everything a full turn to see if it's always like that or if there are tight spots as well.  (Maybe loosen the mag fixing bolts and nudge things?? I know you've put the cover back on  . . . . but many of us  have suffered fibre drive gear failure, and it is a pain when it happens.)
Bill

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Re: Points gap question
« Reply #22 on: 09.12. 2018 20:19 »
mod edit: post split from "ATD fibre teeth". Lots of cross-topics ongoing these days...


No dammit, I can't go to sleep ( sorry dear, I'll turn the light off shortly).

HOW THE HELL CAN THE BIKE RUN WELL WITH ONE POINT GAP OF 0.09" AND ONE OF 0.19"??!

(You may need to read my parallel post in the electrical section).

Surely it should be running like a bag of poop?  I JUST DONT GET IT! *pull hair out*

The critical issue is the timing, not the points gap. It may be that, even though the gaps are uneven, the timing is OK. Check the firing position on both cylinders with a degree disc or plug hole probe. You may find that the firing points are virtually the same, in which case the bike will run fine. Even if the firing positions are slightly different the bike may run fine but slightly hotter on one side. They're very forgiving, these A10's!!     A .010" imbalance is quite extreme and the points on the wide side will suffer from 'hammering' as 0.019" is a bit too big and it means the points are working like your hands clapping very loudly, i.e they'll get sore after a while. 0.009" is not so bad as Lucas were happy with 0.010" anyway, but if you get down to less than 0.008 (ish) you run the risk of arcing when the points separate, then it will run crap!
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline a10gf

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Re: Points gap question
« Reply #23 on: 09.12. 2018 22:13 »
My old research into uneven points gap \ uneven timing >
https://www.a7a10.net/forum/index.php?topic=1375.msg9862#msg9862

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Online beezermacc

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Re: Points gap question
« Reply #24 on: 09.12. 2018 22:40 »
A10gf's previous article makes good reading and it is certainly true that by fitting the bearing in an eccentric position can resolve the problem. An imbalance of 0.010" is worth redressing. The fundamental cause of the problem is either a poorly machined cam ring or a poorly machined cam ring housing. In most cases the cam ring is OK. However the cam ring housing can be poorly machined a number of different ways..... including offset bearing housing, crooked, i.e face and back not parallel, offset cam ring housing, loose cam ring in housing (often the case with manual mags). Another common problem is that the cam ring housing is a poor fit on the body which causes the armature to run out of line with the body.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline a10gf

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Re: Points gap question
« Reply #25 on: 09.12. 2018 22:53 »
In my case, the mag was seemingly made from some parts of different sources, resulting eccentricity was not an unexpected find. To be clear, camring, bearing and points were fine, the camhousing itself was what was slightly out of line with the magneto body.

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Offline RichardL

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Re: Points gap question
« Reply #26 on: 09.12. 2018 23:25 »
My old research into uneven points gap \ uneven timing >
https://www.a7a10.net/forum/index.php?topic=1375.msg9862#msg9862

A "must read" for anyone with asymetrical points gaps, even if not due to this particluar cause.

Richard L.
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