Author Topic: A7 magneto problem  (Read 2168 times)

Offline BSA500

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A7 magneto problem
« on: 03.03. 2009 15:35 »
This problem came about due to a loose bolt.The centre bolt that holds on the contact breaker assembly worked loose today.During its daring dash to escape it has shattered the plastic baffle(bin),not so bad( I will have to live with it as cash poor at the moment) but the points base plate,the brass type,has had the key flattened.I can just about line it up by eye but it seems to be running a little retarded.The bolt is loctited in.Can this key be reinstated by tweaking it out with some method or other.Years ago independent ignition done this for me but as said before am a little poor at the moment and brass cb plates are quite rare anyway.

Andy

Online groily

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Re: A7 magneto problem
« Reply #1 on: 03.03. 2009 17:10 »
Andy, I think it'll be an awful struggle to set the timing up properly and keep it there if the key is dead like the parrot. But it might be possible to unflatten it as follows: take a 7.8mm drill or length of anything rigid, insert the blunt end up the hole. Grind or file something down to get into the small gap you've probably got where the inside of the raised bit for the key has got squashed, and prise gently against the drill's shank to try to get it back - without busting the thing, as it's quite delicate. Jeweller's screwdriver might get it started. You really want the raised bit back for all its length if possible, using a tapered square section spike - with extreme care - driven in against the drill's shank to keep it on line.
If no joy, I've got one old brass plate you could have - the key's good but there's slight wear on the pivot for the moving point, and it's also missing the little push-fit brass pin that holds the moving point's retaining clip on.
Send me a private mail if you're still stuck when you've tried to unflatten the thing. If you've got all the other bits, something can be done, it always can. Not quite sure what the 'plastic baffle(bin)' is though!
In all events, I think you'll probably have to reset the timing, as it'll be a bit out whatever you end up doing. Loctite on the centre screw could be a problem too - it's only 4BA and loctite's quite strong stuff. Fingers crossed you can get it off again!
Bill

Online RichardL

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Re: A7 magneto problem
« Reply #2 on: 03.03. 2009 17:33 »
Hopefully, blue Loctite.
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Offline LJ.

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Re: A7 magneto problem
« Reply #3 on: 03.03. 2009 20:56 »
I'd have thought loctite would be a no no... the centre bolt does not want insulating and the loctite could do just that. Just a small spring washer would be all thats needed. I dont think any of my bikes have this though.

Just cringing at the thought of bending out that tab... so I'll go fully along with what groily says.... Be really really careful. Good Luck!
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline BSA500

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Re: A7 magneto problem
« Reply #4 on: 03.03. 2009 21:23 »
Hi,
 Thanks for the replies.The baffle is the black plastic/bakalite end cover that has the cut out wire attached(if that makes sense).The thread locking compound(not loctite) is a quite light compound they usually come off quite easily.The drill idea sounds like a goer I shall try that out.A spring washer cannot be used as the bolt has its own taper to lock it against the contact breaker plate.

Online Triton Thrasher

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Re: A7 magneto problem
« Reply #5 on: 04.03. 2009 09:47 »
You didn't ask this, but if the moving point is loose on the pivot pin, strange things can happen to the timing at higher revs.

Online groily

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Re: A7 magneto problem
« Reply #6 on: 04.03. 2009 13:16 »
Ah, I thought the 'plastic baffle(bin)' might refer to the insulator that lines the hole through which the central screw passes, and which has a square section on the rear to hold the wotsit that the wire from the armature comes to . . . if that was dead, that's real trouble as it comes out from the inner end, and requires a partial armature strip-down to replace. Difficult.
The end cap can be bodged up for the time being almost for sure - but if you've got manual ignition control you HAVE to have a cap on the end or the cam ring will fall out. If you've got an ATD it'll hang together . . . until it rains! But there must be many plastic containers that could be cut down to make a waterproof lid!
Triton Thrasher's spot on about wear on the pin and the effect on timing  - but my old and available one was working fine, and worked actually quite well with a new moving cb point. It's just that I had a better one. It would certainly do for a good while, and save having to buy a new unit right now if the taper-straightening exercise goes sick. Although SRM and maybe others do sell brand new steel complete cb assemblies with car-style adjustment, which I don't like as much as the Lucas part.
Bill

Offline BSA500

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Re: A7 magneto problem
« Reply #7 on: 04.03. 2009 15:19 »
Thanks groily if I do happen to cock up the key i shall take you up on the kind offer.I will let you all know how I get on.
Andy

Online Brian

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Re: A7 magneto problem
« Reply #8 on: 05.03. 2009 06:53 »
Here is Aus we have a magneto specialist who does rewinds etc. Anyway, if the key on the points base is gone he stamps a new one at 180 degrees to the old one and problem solved.

I am sure the magneto specialists in the UK would also be able to do this so I would suggest checking with them.

Offline BSA500

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Re: A7 magneto problem
« Reply #9 on: 05.03. 2009 08:37 »
Thanks again for the replies.I have sent an email to Independent ignition here in the UK just to get an idea of price etc.I will have a go at fixing this as other than the key damage this is a very good set with no other wear(dammit),but again I may call on Groily's kind offer if,which really means when,this all goes pear shaped.
Andy

Offline BSA500

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Re: A7 magneto problem
« Reply #10 on: 06.03. 2009 09:20 »
Update....
 I have contacted Independent ignition and they can recut/reinstate the 'feather key' as they call it for £9.78 incl return postage vat etc etc so I shall go with that so thanks again for all the replies and to Groily for his kind offer.
Andy

Online groily

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Re: A7 magneto problem
« Reply #11 on: 06.03. 2009 10:21 »
Well that's good news and not too pricey . . . sounds like a result! Nothing better than having it done right, which it will be.
Bill

Offline BSA500

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Re: A7 magneto problem
« Reply #12 on: 11.03. 2009 20:49 »
Update...
 Sent points to Independent Ignition they emailed Monday to say they arrived,posted back Monday pm arrived Tuesday pm-picked up Weds am as the box is to big for letter box.Installed in under 5 mins starts second kick ready to ride to work tomorrow.Can't fault that service all for a tenner.
Andy

Offline LJ.

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Re: A7 magneto problem
« Reply #13 on: 11.03. 2009 21:07 »
Hey Presto! One happy bunny... Great news.. thanks for the update.  *beer*
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red