1932 BSA side valve starting problem

[Billington]

I hope you can help me, I’m having trouble starting my 1932 W32-6 (500cc side valve).

I’ve have my magdyno professionally rebuilt, in the process replacing the three brush dynamo for a two brush dynamo on the advice of Tony Cooper who did the rebuild. Also on his advice I’ve remove the mechanical regulator coil and replaced it with a modern semiconductor solid state encapsulated regulator for motorcycles using the Lucas E3 type dynamo.

Since the rebuild I have had the bike running and have travelled about 3 miles. However today it would not start; it would only bake fire through the carburettor. This happens irrespective of the position of the ignition control and the air level.

Why will it run one day and not start the next? How can I diagnose and fix this problem.

Thank you for any helpful advice.

[TGR90B]

I would ignore the dynamo as it has nothing to do with the spark. I would suspect that the magneto drive cog has slipped on the taper to the mag. Kick it over and see if there's still a spark. If so it's probably that the timing's slipped as above.
My only experience is with the later Lucas magdynos, so I could be talking out of the proverbial.

[R]

Changing the spark plug (temporarily) for something new and clean may also be a good move, test wise.  Although it does sound more like the timing or spark has gone awol.

[Billington]

Thanks for your posts. The spark plug is new. I also removed the cylinder head to ensure that the timing on the magdyno was correct. On this model the BSA manual of the time indicates the spark should occur at Top Dead Centre when the ignition control is fully retared.

[TGR90B]

Yes, but have you re checked it?

[R]

Likewise, have you tried a new plug since this non-starting business arose.

[Rex]

If you've only gone three miles on it I'm guessing that maybe you haven't established a starting routine yet? All bikes have their foibles when starting; my old Enfield will go second kick, but if it dies (putting on helmet etc) it'll be a sod to restart and does the same tricks, backfiring, etc etc, and even when really hot, it still needs a little tickle to get running again. It's just one of those things.
Maybe you wetted the plug and now it's knackered, and so a replacement is a good idea. Always start with the easy things; as the old joke goes, too many engine rebuilds end up at the spark plug.

[TGR90B]

Or perhaps the jet block in the carb. has picked up a bit of crap in one of the drillings.
Feed back would be appreciated.

[Billington]

Thank you for all your help. Yesterday I had another go at starting the bike. I made no alterations other than trying the ignition level and air lever at different positions (which I had done before).

After two minutes of the same back fire and failing to run it came to life! I quickly put my helmet and gloves on and set off for a ride. For the first mile and a half the engine was popping, but at the two mile mark the engine smoothed out and I started to enjoy a well mannered bike. After four miles I realised that the vibrations were undoing the nut on the ignition lever, hence I returned home before I lost the nut and created another job.

When I got home the bike was running fast at ideal, can I resolve this by turning in or out the air screw on the carburettor?
The bike started when the ignition was fully retired and the air level was full closed. I would like to think that this was to answer to my problem; however I know that I had tried this combination before with no luck.

What do I take from this small victory to the journey to understanding my bike and having an easy to start smooth running bike, ……. well just these points:

1, Air fuel is getting through to the engine
2, The new spark plug works fine
3, The engine timing works

[chaterlea25]

Hi,
The "book of the BSA" will include instructions on starting and riding your W32-6
reprints are available or to download

https://www.mlr.press/release10/03-prof-maryse-reichel/9bflkKxiLa-the-book-of-the-bsa-an-owners-workshop-manual-fo-doc.pdf

https://www.amazon.com/BOOK-BSA-WORKSHOP-PRE-WAR-MOTORCYCLES/dp/1588500462

John

[Billington]

Hi John

Thank you for your post. I have a copy of this book and have found it to be useful. I also have the B.S.A Motor Cycle Instruction Book 1930 to 1936 which tends to covers my bike more closely.

This has been my first reference for stating the bike, however it’s method currently does not work.
Just for interest the book says.

Set the throttle at about one eighth open and the air lever shut. Move the ignition control to about one half full advance.

With the larger engines, first depress he kick-starter until compression is felt. Then raise the exhaust lifter and depress the kickstarter about another quarter of its travel. Allow the kickstarter to return to its top position, and without rising the exhaust lifter give the pedal a vigours kick downwards. In cold weather flood the carburetter by depressing the tickler for a short time only, since excessive flooding will make starting difficult. Now move the ignition control to the fully advanced position. As soon as the engine is warm open the air lever about three-quarters of its travel. It is unnecessary to disturb this control unless the engine knocks when the control should be closed slightly.

[R]

As said above, engines are  always (almost always ?) set so the spark timing is a certain number of degrees or fractions of an inch (or mm) before tdc fully advanced - and the retarded value will take care of itself.
So that is/was most of your real problem all along... ?

You need to research this further, it would be odd if BSA had suddenly discarded decades of experience in quoting this value ?

My bikes - not W32-6 though - will not start if fully fully retarded, the spark has faded a bit by then.
So your spark may be a bit weak by the time its fully advanced ?
You likely won't find this out until conditions (inside t'engine) are tougher...

[chaterlea25]

Hi Billington,
I never bother with  the air lever on my bikes, from cold press the tickler until fuel spills
a hint of throttle, and as much advance as possible without kick back
As R said the spark fades with retard
Some old sidevalvers need a good spinning over to fire especially when hot
Some riders spin the engine  with the valve lifter operated and drop it (at the right moment) so the flywheel inertia
starts the engine
Its all getting to know the beast involved

John