The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: roadrocket on 05.08. 2018 12:04

Title: Points shorting through fixing bolt
Post by: roadrocket on 05.08. 2018 12:04
Hello,

I wanted to check ignition timing after a short ride yesterday, which suggested that it was not spot on. It would pink and die at idle. Sure enough upon using my ignition timing lamp and piston position indicator it showed retarded ignition. Points gap was to big too. That fixed (brass points plate), I checked timing again, but now there is constant contact between points when the points plate fixing screw is in place. Points plate off I checked if the points would break between plate and fixed point, which it did. I put the plate back in the magneto, without the fixing screw, and still the points would break. But when I put the fixing bolt back in, there was now constant contact, points open or closed. What could have happened?

Title: Re: Points shorting through fixing bolt
Post by: roadrocket on 05.08. 2018 12:35
Update: even when the timing device (smart job made by Dave Lindsley using AC I think) shows continuity when points are open, the bike fires and runs. But I cant time it using the device when it no longer show when points are opening. The device itself is fine, showing a red light when the probes are held together, no light when no contact.
Title: Re: Points shorting through fixing bolt
Post by: Triton Thrasher on 05.08. 2018 12:36
Sounds normal.
Title: Re: Points shorting through fixing bolt
Post by: berger on 05.08. 2018 13:37
I have not been to the pub, as triton thrasher says this is correct as I found out years ago trying to use a AVO amps volts ohms meter to see when points open {testing for a continuity break} . you can't do it with a mag, I phoned the guy who had re-wound the armature thinking something was wrong and he said use the old fag paper method and everything was fine , going to give my betsy a blast today shes been lonely while ive been on the *** *beer*
Title: Re: Points shorting through fixing bolt
Post by: roadrocket on 05.08. 2018 14:10
The device I am using is specially designed for mags. It has a 9 volt battery, and uses AC. It has been used with succes by me lots of times.
Title: Re: Points shorting through fixing bolt
Post by: JulianS on 05.08. 2018 15:14
the mag timing devices do work very well.

Suggest fully dismantle the pints assembly and ensure all the insulating washers and shimw are in position and that the points are in good order, sometimes the contact face of the moving point comes loose.
Title: Re: Points shorting through fixing bolt
Post by: Triton Thrasher on 05.08. 2018 15:18
Does the magneto produce a spark?  Can’t be much wrong if it does, so don’t try to fix a non-problem.

Time it by the cigarette paper method.
Title: Re: Points shorting through fixing bolt
Post by: chaterlea25 on 05.08. 2018 15:48
Hi,
I would suggest that you are not connecting the timing device properly  *????*
One lead to the points rotor centre bolt and the other to the mag body

John
Title: Re: Points shorting through fixing bolt
Post by: roadrocket on 05.08. 2018 17:07
Thanks folks, somehow I was later able to se the light (as they say). I have used the device many times, so know how it should be connected. What happened I can't say.
Title: Re: Points shorting through fixing bolt
Post by: bsa-bill on 05.08. 2018 17:31
Quote
Thanks folks, somehow I was later able to see the light (as they say).

Welcome to the world of the inconsistently illuminated, the light does come on but not always immediately when the switch is thrown.
Keeps us humble, re-enforces partly forgotten memories, smile with similarly inflicted - and is much fun - right
Ask me how I know  *smile*