The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => Lucas, Ignition, Charging, Electrical => Topic started by: mike667 on 02.05. 2010 22:12

Title: Mag replace time - helpful suggestions
Post by: mike667 on 02.05. 2010 22:12
Hey all
   well i think my maggie is about to give up the ghost. it is becoming increasing hard to start  my A10 when it gets hot, today was a real chore after a 40 mile ride  and required a few (to many) pints to allow it to cool , then she fired right up, at least it was only a 10 minute ride home....

 so my question is -  any pointers to follow, as this is unknown territory for me- or is the haynes manual pretty good?

i have a rebuilt mag already - figure i need a gasket for it  & the timing cover (hoping the gasket on the cover is fine but since have to order all my parts and want to minimize downtime) - also i has going to try to do the TDC with a graduated pipette set up like in one of the other topics for timing rather than open the primary up 
 any pointers would be great
 thx
 mike
Title: Re: Mag replace time - helpful suggestions
Post by: MG on 03.05. 2010 09:26
Hi Mike!

The Haynes manual explains everything pretty well as far as I can remember, just can add a few hints here:

If you have auto advance, you have to wedge the mechanism open to full advance. For this purpose two reversed clothes pins work a treat.
If you have to take the mag out anway, you might want to consider changing the fibre gear to an aluminium one. These are available for hand and auto advance versions, the latter requiring disassembly of the advance unit and fitting the gear with new rivets. No big deal really. The question with the fibre gear is not IF it will break, but WHEN it will.
If you have managed to get the timing somewhere close to where it should be, a small remaining deviation can be fixed by adjusting the points gap. A smaller gap will set the spark a bit later, a larger gap will set it earlier accordingly. The gap should remain in the region between 12 and 15 thou however! So this is really only a method for fine-tuning.

HTH, Markus
Title: Re: Mag replace time - helpful suggestions
Post by: mike667 on 03.05. 2010 11:30
Hi Mike!

The Haynes manual explains everything pretty well as far as I can remember, just can add a few hints here:

If you have auto advance, you have to wedge the mechanism open to full advance. For this purpose two reversed clothes pins work a treat.
If you have to take the mag out anway, you might want to consider changing the fibre gear to an aluminium one. These are available for hand and auto advance versions, the latter requiring disassembly of the advance unit and fitting the gear with new rivets. No big deal really. The question with the fibre gear is not IF it will break, but WHEN it will.
If you have managed to get the timing somewhere close to where it should be, a small remaining deviation can be fixed by adjusting the points gap. A smaller gap will set the spark a bit later, a larger gap will set it earlier accordingly. The gap should remain in the region between 12 and 15 thou however! So this is really only a method for fine-tuning.

HTH, Markus


awesome thx Markus!
Title: Re: Mag replace time - helpful suggestions
Post by: a10gf on 03.05. 2010 21:23
Not to promote my own topic, but you may find some interesting content in http://www.a7a10.net/forum/index.php/topic,1375.0.html

The mag dying when hot, very probably an armature failure. Also check the capacitor.
Title: Re: Mag replace time - helpful suggestions
Post by: BSA_54A10 on 06.05. 2010 04:20
Check the brushes.
My very first BSA was a really quick A 10, for about 1 hour, then it would start to miss & fart & carry on.
Being the "cool & cleaver " 18 y old that I was I naturally checked the float, set the tappets, cleaned the slip ring, checked the timing after which it would fire up and run like a top ,,,,, for another hour or so.
In due course it was discovered that if I did absolutely nothing, it would start again in 15 to 20 minutes so I took to stopping for a burger or smoke or whatever every hour or so.
Eventually it died all together right in front of a sparkie so I went in & bought a new set of brushes ( as they were very thin) but when I went to fit them they were different to what was in there so I took them back to get the "correct ones".
He asked if it would miss when really hot & I was miffed as to how he knew.
"Always happens with Bosh brushes in a Lucas pick up " was the reply.
Ever since then I have been very particular about brushes and most times I look at some ones bike it has either the wrong brushes, or cheap & nasty inferiour imported brushes.
Title: Re: Mag replace time - helpful suggestions
Post by: mike667 on 09.05. 2010 11:41
Check the brushes.
My very first BSA was a really quick A 10, for about 1 hour, then it would start to miss & fart & carry on.
Being the "cool & cleaver " 18 y old that I was I naturally checked the float, set the tappets, cleaned the slip ring, checked the timing after which it would fire up and run like a top ,,,,, for another hour or so.
In due course it was discovered that if I did absolutely nothing, it would start again in 15 to 20 minutes so I took to stopping for a burger or smoke or whatever every hour or so.
Eventually it died all together right in front of a sparkie so I went in & bought a new set of brushes ( as they were very thin) but when I went to fit them they were different to what was in there so I took them back to get the "correct ones".
He asked if it would miss when really hot & I was miffed as to how he knew.
"Always happens with Bosh brushes in a Lucas pick up " was the reply.
Ever since then I have been very particular about brushes and most times I look at some ones bike it has either the wrong brushes, or cheap & nasty inferiour imported brushes.

interesting! thx
Title: Re: Mag replace time - helpful suggestions
Post by: mike667 on 29.05. 2010 00:31
Guys/Markus
  thanks for input -  the bike fired up first kick (!!) w/ the new mag and ran fantastic - i used Richards learning by degrees thread and set the bike up a hair over 5/16  as a starting point. don't think i want to change a thing though as it runs sweet and pulls up to 80 mph with no hesitation and no kickback on startups .

 only thing left to do to it  is readjust the dynamo chain - i put a new one in and must have it a bit to loose as it seems noisier than previously - still pumped up about it - going to drive for a long distance trip this 3 day weekend- yippy!

m
Title: Re: Mag replace time - helpful suggestions
Post by: MG on 29.05. 2010 08:59
Congratulations, good work.

Have fun on your trip!