The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Tumbleweed on 28.08. 2013 12:34

Title: k2f mag kill button
Post by: Tumbleweed on 28.08. 2013 12:34
hi , everybody, i have just had my mag repaired and now the kill button dont work, i have read thro the letters but i cant see the same prob , with the cap off the bike  there is no continuity between the frame and the carbon brush untill i press the kill button , i wonder if the repair is the fault , the bike starts ok but wont stop unless i stall the engine ,   any ideas would help im sure.   thanks  tw
Title: Re: k2f mag kill button
Post by: duTch on 28.08. 2013 14:47

 Maybe the carbon brush isn't contacting inside, and needs to protrude a bit further..??
Title: Re: k2f mag kill button
Post by: A10 JWO on 28.08. 2013 16:06
I had the same problem. I contacted one of the experts in OBM who rebuilds them. He sent me a new spring and carbon brush FREE OR CHARGE. I sent him half a dozen first class stamps for his trouble.
Colin
Southend
Karma 0
Title: Re: k2f mag kill button
Post by: Tumbleweed on 28.08. 2013 19:54
i will check these things , thanks folks
Title: Re: k2f mag kill button
Post by: morris on 28.08. 2013 21:58
I sent him half a dozen first class stamps for his trouble.
Colin
Southend
Karma 0
A bloke who sends half a dozen stamps out of gratitude can't be bad.
Cheers and enjoy your first karma point *smile*
Title: Re: k2f mag kill button
Post by: trevinoz on 28.08. 2013 22:11
Is your earth brush on the drive end OK?

Trev.
Title: Re: k2f mag kill button
Post by: A10 JWO on 29.08. 2013 15:24
The brush & spring is on the same side as the kill cable, just unscrew the large cap, it is behind it. Mind that nothing falls out ?

Regards Colin
Southend
Title: Re: k2f mag kill button
Post by: muskrat on 29.08. 2013 21:57
I'm sure that Trev means the earth brush under the screw at the mounting flange end.
Cheers
Title: Re: k2f mag kill button
Post by: trevinoz on 29.08. 2013 22:22
That I do.
Title: Re: k2f mag kill button
Post by: Tumbleweed on 30.08. 2013 11:32
hi folks, i have tried spring tretching and cleaning but it is still the same, i took the cap off and earthed the centre bolt to the engine  and i am getting a small spark but the engine still wont stop  *conf*  tw
Title: Re: k2f mag kill button
Post by: A10Boy on 30.08. 2013 13:23
Did you check BOTH brushes mentioned above? the one in the points cover cap can fall out if the cap isnt on properly. the other is under a brass screw near where the mag bolts to the engine. Both must be good.

Title: Re: k2f mag kill button
Post by: A10 JWO on 30.08. 2013 16:18
For what it is worth, some people who don't have kill switches simply tickle the carb ( hold it down ) this will also stop the engine. Not tried it myself.

Have a nice weekend.

Colin
Title: Re: k2f mag kill button
Post by: Triton Thrasher on 30.08. 2013 18:05
Earth brush is first suspect when this happens.  The earth brush is not the brush in the cap.
Title: Re: k2f mag kill button
Post by: Tumbleweed on 30.08. 2013 19:50
thanks folks, both earth brushes are about half in long and look ok to me the button was working before i had it done up , but wouldnt start, now it starts so easy but wont stop  *sad2* yes i had better forget   it over the week end ,( her indoors is complaining about the long face already) cheers   ,tw
Title: Re: k2f mag kill button
Post by: Triton Thrasher on 31.08. 2013 07:46
Is an earth brush that long?

You didn't take out the HT pickups instead, did you?
Title: Re: k2f mag kill button
Post by: Tumbleweed on 31.08. 2013 08:14
 just measured them properly and they are only quarter inch (sorry must be a bloke thing), i recently fitted a solid state reg, i wonder if thats the problem . tw
Title: Re: k2f mag kill button
Post by: Brian on 31.08. 2013 08:30
When you say they are BOTH about 1/4" long what do you mean ? There is only ONE earth brush, not two.

The one you need to check is at the front of the maggy under the screw in the picture I have added.

If this earth brush is ok then the fault has to lie with the brush in the cap or with the kill button itself.

Title: Re: k2f mag kill button
Post by: duTch on 31.08. 2013 11:01

 T-Dub, can't see how anything related to regulator will affect it ......? more the likely earth brush factor....
Title: Re: k2f mag kill button
Post by: Triton Thrasher on 31.08. 2013 12:56
When you say they are BOTH about 1/4" long what do you mean ? There is only ONE earth brush, not two.

The one you need to check is at the front of the maggy under the screw in the picture I have added.

If this earth brush is ok then the fault has to lie with the brush in the cap or with the kill button itself.



Don't some have an earth brush behind the points plate?
Title: Re: k2f mag kill button
Post by: wilko on 01.09. 2013 00:50
Yes.
Title: Re: k2f mag kill button
Post by: trevinoz on 01.09. 2013 21:58
But not necessary.
Title: Re: k2f mag kill button
Post by: duTch on 02.09. 2013 09:11

 Amazing how many Brushes there are in a Maggie, 1 for each plug wire=2, + 1 earth brush + 1 cut-out/kill brush + 1 behind (some-Trev?) points plates.

2+1+1=4+1(?)=~5.....any more we forget about.??

     *smile* *eek*
Title: Re: k2f mag kill button
Post by: Tumbleweed on 02.09. 2013 15:44
hi , everybody thanks for your input, it still wont stop ive looked at the things that were mentioned, exept i cant remember a brush behind the points plate, would it be easily seen when the plate is removed,and  is it a carbon brush    ? *conf*
Title: Re: k2f mag kill button
Post by: trevinoz on 02.09. 2013 22:26
The brass point plates had a brush on the rear originally but this was done away with when the steel plates came into use.

Trev.
Title: Re: k2f mag kill button
Post by: Tumbleweed on 03.09. 2013 21:21
thanks , this one has steel plate trev , its running so well just now i think i will settle for stalling it for the time being  i am glad the reg has nowt to do with that prob  *smile*  tw
Title: Re: k2f mag kill button
Post by: KenF on 04.09. 2013 08:41
TW, if the engine will still run with the contact-breaker centre-screw shorted to the mag housing, then I think you're asking for trouble by not sorting it. The earth brush isn't doing its job properly. That could mean that the sparking plug return current is having to spark across one of the bearing insulators, which won't do it any good, and then pass from the bearing outer race to the inner race through the balls and grease between them, which in the fullness of time will wreck the bearing.

If you've got a multimeter that will measure resistance down to 1 ohm or less, then measure the resistance between the CB centre-screw and the mag housing. It shouldn't be more than about 10 ohms. If it is, do whatever you need to do to the earth brush and its spring to get the reading down to 10 ohms or less.

And once you've done that, you'll probably find your cut-out works again.

Best of luck,

Ken
http://www.brightsparkmagnetos.com (http://www.brightsparkmagnetos.com)
Title: Re: k2f mag kill button
Post by: Tumbleweed on 04.09. 2013 16:19
thanks ken, my next door neibour , came round with his multimeter, and it read 85.5 ohms, ive cleaned the earth brush again, starts first kick but still wont stop on the button *sad2*
Title: Re: k2f mag kill button
Post by: Triton Thrasher on 04.09. 2013 18:56
Is the earth brush spring making poor contact with the little cupped screw it sits in? Rust, grease or something in it?
Title: Re: k2f mag kill button
Post by: wilko on 05.09. 2013 00:23
Can't wait to get to the bottom of this?
Title: Re: k2f mag kill button
Post by: KenF on 05.09. 2013 06:51
85 ohms is the problem, TW. As TT says, check that the spring-to-cup contact is good. If it is, then the 85 ohms suggests, as British Rail might have said, that your earth brush is the "wrong type of carbon." Send me your address to ken@brightsparkmagnetos.com, and I'll pop a replacement in the post to you. Or if you'll be at Netley Marsh on Friday or Saturday, come and see us in the marquee.

Ken
http://www.brightsparkmagnetos.com (http://www.brightsparkmagnetos.com)
Title: Re: k2f mag kill button
Post by: Tumbleweed on 05.09. 2013 15:14
hello everybody,  at last a result , not only does it start 1st/ 2nd/ kick it also stops on the button,thanks to all your help.   I have cleaned/ scrubbed/ filed the earth all to no evail , taking note of how important the earth is ,i tested the carbon brush with my trusty  tester and a current wouldnt pass thro so i found another carbon fitted it  and hey presto problem solved (thanks for your offer ken) , wilko can rest now. what i cant understand is its the same brush that was in befor i had it repaired and it worked, they perhaps pack up suddely,     once again thanks everybody, great learning curve  *smile* *smile* tw
Title: Re: k2f mag kill button
Post by: trevinoz on 05.09. 2013 21:55
TW,
            Possibly a film of grease has impregnated the brush and caused the high resistance.
Maybe a bit of a rub with an abrasive on the working end may fix it.

Trev.
Title: Re: k2f mag kill button
Post by: Triton Thrasher on 05.09. 2013 21:57
Love it when someone gets a result.

Has the old brush been carved from some sort of resistor?
Title: Re: k2f mag kill button
Post by: wilko on 06.09. 2013 01:20
I had a Mag that somebody carved a pickup brush out of plastic?? I should have suggested another brush!
Title: Re: k2f mag kill button
Post by: duTch on 06.09. 2013 08:12


 Yeah, but if you had it repaired, how can you be sure it's the same brush that it had?? Maybe the repair shop got some bits 'mixed'..?
Title: Re: k2f mag kill button
Post by: muskrat on 06.09. 2013 10:29
Good onya TW, great to see it's sorted.
Many moons ago I replaced the earth brush (same problem, couldn't stop it) with a carbon center of a C size battery. It lasted for about 10 years.
Cheers