The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: bsaketcase650 on 24.03. 2009 12:14

Title: Help with ignition timing - 1960 A10
Post by: bsaketcase650 on 24.03. 2009 12:14
I have recently reached the very latter stages of my restoration of a 1960 A10 . This has included a nut and bolt rebuild of the engine including a reconditoned auto advance mechanism, rebuilt magneto and new carb.
That said,  I am somewhat confused regarding the iginition timing setting for this bike. The factory service sheets state that for A10 GF with frame numbers prefixed with GA the timing should be 13/32 BTDC full advanced. Haynes manual states 11/32 and the SRM website states 9/32 to take account of unleaded fuel. I initially set the timing as per the factory service sheets and whilst the engine started and ran ok it was a little sluggish to pick up on the throttle. Given that I have had hardened valve seats inserted to take account of modern fuels I decided to re-set the timing as per SRM's recommendation. The engine now is very difficult to start and runs very rough. Please can someone tell me the best figure for the ignition. Any help or advice would very welcome.
Title: Re: Help with ignition timing - 1960 A10
Post by: Brian on 24.03. 2009 12:57
I run mine with 5/16" advance. That is slightly less than what the book says but with modern fuels you can have trouble with pinging. The valve seats have nothing to do with the timing, its all to do with pinging caused by most modern fuels. Basically most unleaded fuel is rubbish.

When you set your timing make sure you jam the auto advance unit in the fully advanced position. I use a small piece of wood cut into a wedge shape.
Title: Re: Help with ignition timing - 1960 A10
Post by: bsaketcase650 on 24.03. 2009 16:27
Thanks for that Brian.

I'm beginning to realise what a fiddly job it is trying to hold the magneto points in position whilst trying to gently tighten up the automatic advance unit.  Having looked through this forum I can see the problem is a fairly regular topic!

Title: Re: Help with ignition timing - 1960 A10
Post by: MikeN on 24.03. 2009 19:31
I set mine to 5/16" and I have had no probs (manual ign) although my neighbour  has gone to 3/16 (ATD) and hes still not happy with it. we've both got alu heads and L/Free conversions.
Title: Re: Help with ignition timing - 1960 A10
Post by: RichardL on 24.03. 2009 19:56

This morning, when I first saw you were working on timing, I thought about sending the following quote from one of my own posts to you but, then, thought you might think me full of myself or "it." Considering your latest post, I now think I might be giving some honest help by sharing it. This will give others the opportunity to declare that I am full of the latter, or both, or perhaps they will agree.


There is a boatload of talk and suggestions here in the forum about measuring BTDC with the head in place. My own apprach, you may recall, was a straw with a taped-on graticule and which ran into the plug hole through a guide clamped to the head-steady bracket. I'd steer you to photo if need be. It seemed to work well.

About tightening the ATD unit without changing the timing, I have started to get a little feel for this and think I have made progress over the last time I did the timing which took about 15 tries.  First, I got sick of messing with the horseshoe washer so I cleaned the large washer (having two alignment holes) and the horseshoe washer with mineral ("white") spirits and sprayed one side of the horseshoe washer with a light coat of contact adhesive. This keeps it in place so you can concentrate on the hold-down bolt. (I don't think anyone can convince me that the possibility of this small amount of adhesive working its way into the oil as a clogging factor is a problem.) Once you have the timing set, finger tighten the bolt while applying back pressure at the points plate with the other hand. Now, with the socket over the bolt, and no ratchet or breaker-bar in it, very lightly tap the end of the socket. Now, with the ratchet or breaker, make a first light tightening of the bolt, to the extent you can, summon-up all possible thumb strength and try holding back some of this turning at the points plate. Now, recheck the timing. If good, go ahead and finish tigtening the bolt. Recheck timing again.

Richard L.

Title: Re: Help with ignition timing - 1960 A10
Post by: bsaketcase650 on 24.03. 2009 20:26
Thanks Richard.
Appreciate any help or advice on this sticky issue. I'm sure that with continued practise I will get the hang of it - after a lot of 'effing and blinding'!!

Title: Re: Help with ignition timing - 1960 A10
Post by: BSA_54A10 on 28.03. 2009 00:08
A little trick you might like to try with setting your timing.
Opening the points gap will advance the timing while closing it will retard the timing.
The slip ring can accomodate quite a big variation ( but there is a limit).
So to experiment with different timings simply change your points openings.
When you find the "best" spot, pull the plug and measure the piston drop where the points just open.
Reset the points to the correct opening and rotate the armature as you normally would to time the engine.

Now repeat the whole process to fine tune.

The other little advantage doing things this way which I forgot to mention is that you will end up with a piston drop timing your engine on full retard. This is no big deal with manual advance but dose make life a lot easier for those with aa units. 
Title: Re: Help with ignition timing - 1960 A10
Post by: orabanda on 28.03. 2009 01:00
In order to be able to easily set the timing, and find the best settings for each of my 6 A10's I am taking this approach.
First, I have had my friendly local machinist slot the 3 mounting holes in the mag. It can be done several ways. He set them up in a CNC lathe. the set up was the longest part of the job (about an hour).

He did the auto advance units fully assembled; I stripped the manual advance mags and gave him the casings only.

This gives 19 - 20 degrees of variance of the timing.

I purchased the SRM timing wheel / cush drive nut / piston stop kit, and additional nuts (enough for all my bikes), and made an indicator which screws into one of the casing screws.

For my 54 GF, I set the timing at 35 degrees BTDC using feeler gauge, with the mag in the middle of its adjustment range. Then checked timing with strobe light (had to make a minor adjustment). With the strobe light, it is easy to compare the timing on each pot (cam ring / mag variance).

I have the first of my bikes booked in for a dyno tune in three weeks ($200 - $250; money well spent!), and after removing the primary cover and re-fitting the timing disc we will alter the timing until the bike produces max torque.

I intend to dyno tune all of my bikes, and will post the final timing advance setting for each of them.

Title: Re: Help with ignition timing - 1960 A10
Post by: olev on 28.03. 2009 11:07
gday orabanda,
good on you, you're worth breeding off. most people only put their vintage racing machines on the dyno looking for maximum power. Standard machines don't get a mention.
please post the torque and power curves if you can. I've searched all over for these without much success.
i hope one of these machines will have your 'you beaut' electronic advance BTH bolted on. It would be good to compare its power and torque against an auto centrifugal advance up to 4000rpm or so. and with that SRM timing wheel it wouldn't be too hard to lay an optimum manual advance curve over both of them. also do you have beeza bills email. I am hoping to buy one of his roller cam plungers but his web site seems to have gone aot in the last couple of days.
Title: Re: Help with ignition timing - 1960 A10
Post by: orabanda on 28.03. 2009 11:49
We're on the same wavelength.
The local Suzuki dealer is an excellent mechanic, and had a big investment in his dyno.
Here is the performance graph for my DT360A


The dyno tune gained nearly 2 hp, and the bike has never run better!

These are rear wheel HP.

Here is the bike, next to my '54 GF (destined to be dynoed soon) at a recent toy run.


I have invested so much time, money and love in my bikes that the small amount of money on the dyno doesn't matter when I know they will be running at their optimum, and are jetted and timed as godd as they can get. I ride my bikes, and have a (growing!) group of friends who I encourage to ride them with me on runs, so that they can be seen AND heard!

Therefore, they must perform well, and start easily!

My philosophy is that if I wanted to ride around Australia tomorrow on any of the fleet, then the bike should be up to it!

In last year's toy run, I had 10 bikes on the road.

All of the bikes in this shot were out of my shed.


The Super Rocket with the BTH electronic maggy will be running in 3 - 4 months, and it will be interesting to see how it performs in contrast to the K2F bikes.

Stay tuned (pardon the pun)!

Title: Re: Help with ignition timing - 1960 A10
Post by: a101960 on 28.03. 2009 16:59
Judging by the amount of interest the subject of ignition timing has generated it would appear that this is particular task generates much confusion and puzzlement to all of us. For my part I have consulted with many people and have had a bewildering number of different and contradictory answers to my questions.
My magneto cam ring and housing have been sent away to have the accuracy or otherwise of the lobes checked and for corrective work to be carried out if required. I have had the problem of one cylinder burning weaker than the other. In an attempt achieve an even burn on both cylinders I fitted an anti bias gasket which did not seem to make that much difference. I was told by the guy that is doing the cam check that in his opinion the anti bias gasket was BSA's way of trying to remedy any short comings in the original Lucas machining process, and he may well be right. Everything was built down to a price. This allegedly is how the concentric carburetter came to be introduced (pressure from the factories and BSA in particular) to get the cost down. There was another factor that compromised quality in those days: Piece work. Piece work was endemic in British manufacturing and this led to people striving to reach the specified target not in order to earn a bonus, but in simply to make a living wage. If your weekly wage depended on you attaining a set production target then quality might well be secondary to quantity. It would also be unlikely that there would be anything like 100% inspection so the chance of non compliant components finding there way to the production would be quite high.
Title: Re: Help with ignition timing - 1960 A10
Post by: bsaketcase650 on 29.03. 2009 20:13
Wow - this subject is clearly one that generates a lot of discussion!

Thanks for all the replies and suggestions. I suspect that there are a number of variables involved that each engine may well have it's own particular characteristics, setting each apart from others of the same model. I can only conclude that the various recommended settings for ignition timing are a general guide only and what may be good for one machine may well be useless on another. After much fiddling about mine seems to be now running fine with a setting fractionally greater than 5/16 BTDC.