Starting on Full Advance

[tommo903]

Hi,

I'd be the first to admit that I'm not the most clued up on magnetos...hence my question!

I've had problems starting my recently acquired a 1954 B31 (plunger), but discovered yesterday it's simply because I've been retarding the A/R lever. If I leave it in the fully advanced position (tight wire), it starts instantly.

Is this an issue and does it indicate that the ignition timing will need looking at? It's early days yet and not had chance to check the points and gap, etc.

Thanks,
Steve

[CheeserBeezer]

If the ignition is timed correctly, the strongest spark is achieved at full advance. The more you retard the lever, the weaker the spark gets. Most 'manual ignition' bikes won't start at all on full retard because the spark is so weak it won't spark under compression. However, if the ignition is timed correctly it is likely you get a violent kick-back if you attempt to start the bike on full advance so, in normal circumstances, you would expect to retard the ignition a bit, or a lot, to avoid the unpleasantry of being kicked back by your bike. Most owners of bikes with manual ignition get to know where best to set the ignition lever for starting the bike to achieve starting but, at the same time, to avoid being kicked back. I would advise you check the ignition timing as you need to know whether it is correct or not, then maybe try starting the bike with the lever mid-way between full advance and full retard.

[Roger (Doomtrainbarx)]

"Tight wire" is usually retarded - it is on my Super Rocket anyway.

[muskrat]

G'day Steve.
As Roger said "tight wire = retarded". This is assuming you have the right mag. Anti clock direction, cable entering cylinder side.
So starting with a tight wire is retarded.
Follow CB's advice and check timing & points.
Cheers

[Triton Thrasher]

Not all BSA singles had slack wire advance.

You are advancing the ignition when you are rotating the cam against the points rotation direction.

Yes, check your ignition timing. Set the points gap first. 

In fact, why not do all the service items!

[CheeserBeezer]

"Tight wire" is usually retarded - it is on my Super Rocket anyway.

...MO1's can be either tight or slack wire advance. This is a B31, not a twin.

[KiwiGF]

Hi,

I'd be the first to admit that I'm not the most clued up on magnetos...hence my question!

I've had problems starting my recently acquired a 1954 B31 (plunger), but discovered yesterday it's simply because I've been retarding the A/R lever. If I leave it in the fully advanced position (tight wire), it starts instantly.

Is this an issue and does it indicate that the ignition timing will need looking at? It's early days yet and not had chance to check the points and gap, etc.

Thanks,
Steve

I have a B31 and always retard the ign for starting, to avoid the possibility of kickback. It starts ok retarded or advanced.

On my bike you lose a lot of power and available rev range if you try to ride with the ign retarded, I can retard it slightly for slogging up hills in top, otherwise it stays full advance until I stop and use neutral. I then use the retard lever to slow the tickover and minimise the crunch going into 1st.

The above should help in deciding if your timing is wrong, and which way is retarded and which advanced, but it would be a good idea to check it anyway.

[groily]

As Roger said "tight wire = retarded". This is assuming you have the right mag. Anti clock direction, cable entering cylinder side.

Thought that covered it?

[Triton Thrasher]

As Roger said "tight wire = retarded". This is assuming you have the right mag. Anti clock direction, cable entering cylinder side.

Thought that covered it?

Only covers it for those weirdos who read the thread.

[groily]

Only covers it for those weirdos who read the thread.

[limeyrob]

Having done many miles on BSA singles I would say start as far advanced as you can without launching yourself over the bars, and yes that is possible if you don't keep you knee slightly bent.  In practice the best seemed to be between 1/4 and 1/3 off full advance.  Full retard is only there to create back fires to annoy cyclists.  If you have a slack wire -retard mag swap it for a taught wire, the vibration will sooner or later retard the ign when you least want it and to stop that the lever has to be too tight to use.  I had this on one bike and did the swap.

[BSA_54A10]

M series have the advance cable at the rear and they are tight wire advance
Early Bs were the same
It was a problem with competition engines if the cable broke or came oose so they changed it , first on Gold Starts then on all of the B series but not the M series
Confirm by taking to points cover off and looking

Cam moving is the same direction as the points rotate = retard
Cam moving opposite to points rotation = advance

The same happens with twin cylinder engines .

Both types of advance ar interchangable andafer 70 years good chance what is ther now is not what was there when it left the factory .
Made worse because M series parts are often that little bit cheaper as are BSA riders .