The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Fred Gassit on 15.04. 2015 09:15

Title: A10 with Distributor Ignition. Help please!
Post by: Fred Gassit on 15.04. 2015 09:15
Hi all.
My father-in-law has a tidy BSA A10 Super Rocket of 1958 or 59 vintage.
At some point in its life it has been rewired, fitted with an electronic regulator, and most interestingly a distributor ignition system.
After a 2 year lay-up due to ill health we are having no success getting it started, and it looks like there is a fault with the ignition (poor sparks).
I have attached some pictures of the conversion and the components.
Can anybody identify this modification and suggest where we can get spares? particularly a new dizzy cap?

Thanks very much!
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Greybeard on 15.04. 2015 09:48
Might be the same as this one: http://goo.gl/jckFjO
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Fred Gassit on 15.04. 2015 13:07
Thanks, we looked at the 18D2 cap, but it seems to be quite different...  *sad2*
Title: Re: A10 with Distributor Ignition. Help please!
Post by: bonny on 15.04. 2015 15:43
What powers the ignition system ? Has the bike an alternator fitted ?
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Beezageezauk on 15.04. 2015 16:04
Hi Fred, 

What are the numbers on the distributor body?  They might give us a clue as to the correct distributor cap.

Beezageezauk.
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Fred Gassit on 15.04. 2015 17:47
As far as I am aware the bike still has the original Lucas 6V dynamo.
There are no obvious markings on the distributor body or on the dizzy cap.
The way the points are secured with really small allen screws makes me think it might be a one-off custom job!
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Triton Thrasher on 15.04. 2015 18:13
The only really common twin distributor was the one on the Fiat 126.

Google up some pictures and compare.


Similar?

(http://i257.photobucket.com/albums/hh236/tritonthrasher/2c8765a0902b29043465a474b1143875_zpsvfdrmsy9.jpg)
Title: Re: A10 with Distributor Ignition. Help please!
Post by: chaterlea25 on 15.04. 2015 20:22
Hi,
The points contacts look oxidised? have you cleaned them?
Looking at what you posted, poses a few questions?
Why two sets of points and a distributer cap ????
With two individual sets of points theres no need for a distributer? has it got two coils wired up?

I would use just one set of points and a twin output coil, and forget about all the palaver with distributer caps *bright idea*

HTH
John
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Triton Thrasher on 15.04. 2015 21:19


I would use just one set of points and a twin output coil, and forget about all the palaver with distributer caps *bright idea*

HTH
John

Does the cam have two lobes? I can't see. Your idea would need two lobes on a half engine speed cam.
Title: Re: A10 with Distributor Ignition. Help please!
Post by: wilko on 16.04. 2015 01:38
With twin points and lobes, there is no need for a rotor and cap? It just needs a plain cover and twin coils. Most unusual setup? And yet there is provision on the shaft for a rotor??? Mish mash of parts.
Title: Re: A10 with Distributor Ignition. Help please!
Post by: KiwiGF on 16.04. 2015 08:18

Have you tried swapping the plug leads over?

As per prior posts you have some options to bypass the dizzie for trouble shooting purposes....
Title: Re: A10 with Distributor Ignition. Help please!
Post by: Fred Gassit on 16.04. 2015 10:33
The only really common twin distributor was the one on the Fiat 126.

Cor blimey guvnor, I think we might have a winner! Well spotted that man.   *wink2*

The points drive cam has a single elongated lobe, so when it starts to open one set of breakers the other set is still held open.
At that point the rotor arm is aligned with the correct cylinder.
There is only a single 6V coil fitted, so the distributor points the spark at the correct cylinder.
The points were a bit dirty, but I gave them a careful scrub with fine emery paper and the DMM said they were making good contact.
With the HT lead from the coil held near chassis I was getting big fat sparks, but with the dizzy hooked up and the plugs held against the head I couldn't see much at all. Hence the focus on finding replacement parts for the distributor.
Must admit I was bemused by the complexity of the twin contact breakers *plus* distributor.
I thought the A10 would be a wasted spark system?
Is there any advantage to converting to single fire? Maybe if you fit a hotter cam or something?
Title: Re: A10 with Distributor Ignition. Help please!
Post by: duTch on 16.04. 2015 11:24

 Without going back to do forensics, did I miss any mention of condensor(s)...??
Title: Re: A10 with Distributor Ignition. Help please!
Post by: KiwiGF on 16.04. 2015 11:35
Hi Fred, the a10 magneto points open every revolution of the crank and a slip ring directs the spark to the correct cylinder so there is no spare spark.

The mag goes at half engine speed but the points cam opens the points twice for each mag revolution.

Title: Re: A10 with Distributor Ignition. Help please!
Post by: Triton Thrasher on 16.04. 2015 18:08
Bike won't start?

Plugs first. Fit new ones.

Tickle the carb more. Then even more.

There will be a condenser somewhere in the LT circuit, between points live feed and earth.

You can tell which HT lead goes to which carb, by the direction of the rotor arm when a set of points is just opening and checking which cylinder has closed valves.

Title: Re: A10 with Distributor Ignition. Help please!
Post by: chaterlea25 on 16.04. 2015 22:26
Hi Again,
AHA!!!
Heath Robinson has been at work  *work* *work* *work*
Looking closely I can see the "Hella" symbol on the points and the soldered in wire connecting them

If you wish to persist with tha distributer cap also replace the rotor *idea*

It would still work with a twin output coil and no dizzy cap,
Years ago I would have said use a Hon*a CD 175 6v coil but where do you find one nowadays?
Ebay of course *smile*
http://www.ebay.co.uk/itm/Ignition-Coil-Honda-CD175-Twin-All-Models-71-78-/191523500671?pt=LH_DefaultDomain_3&hash=item2c97b0b27f

FYI, Fiat 126's died when it rained  *sad2* *sad2* LOL

HTH
John