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BSA M20 electric starter

Hi guys.

Eli, a talented friend of mine, has just finished fitting a starter to his WM20.
No need to press the EX valve lifter, works a charm.

It is based on a Honda ("Magna", I believe) starter with the direction of rotation changed.
I have few more photos, if someone is interested.

This is just a mockup. all will be painted and re-assembled.


Re: BSA M20 electric starter

I wonder what the rivet-counter have to say about this.....

On the other hand, we all don't get much younger, do we?

Re: BSA M20 electric starter

Hi Noam,
It would be interesting to see how it was done, what parts where machined and so on, including some close ups.
I know about at least 2 seniors who are riding M20's and would be happy to install an electric starter.

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Re: BSA M20 electric starter

Hi Noam

A friend in Ireland fitted an electric start kit some years ago to his v twin Bsa after he struggled to start it

His twin port 28/29 Ariel then acted up on the Irish national rally and became extremely difficult to start so much so his hip gave in & resulted in a replacement

He found a cheap Honda starter for the Ariel but the Bsa required an old Volkswagen unit

He did all the machining himself - it is hardly noticeable in both bikes

The result of this is he can ride his bikes again - without they would have become ornaments


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Re: BSA M20 electric starter

Hello Michael and John,

I have few photos, and I will try to upload it tomorrow.
I can ask for few more photos, and if the guy has, he will be happy to share.

Yes, the rivet counters would, understandably not like it,
But the owner of this BSA wants to take his grandkids for a ride in the sidecar every once in a while,
And it became a bit difficult for him to start it every time, so if the options are between let it stand in the shed
Or enjoy it from time to time, I would go for the fun and use. :relaxed:
Any way, it is not un-reversible alteration:

As far as I know, he welded a sprocket to the flywheel nut,
Then he used a kind of a ratchet (a sprocket which moves only one way when turen from its center)
From a "Honda" starter system, which goes on the starter.
Then, the starter turned in the wrong direction, and simply changing the polarity did not do the job,
So he gave it to an electrician to change the fields connections,
And basically, the starter engages directly (via the ratchet/clutched sprocket) to the sprocket on the flywheel's nut.
The alteration to the transfer cover was done to accommodate the system,
And he starts the bike without needing to press the EX valve lifter without any issues.

That is as much as I know guys.
I will try to get more info.

Enjoy your weekend,

Re: BSA M20 electric starter

Hi Noam,

Greetings from Jakarta, Indonesia. I have BSA M20 and would like to have electric starter conversion like you did on your M20. Could you help to share some tips and if there is a kit available in the Market would you also let me know.

Thank you,

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Re: BSA M20 electric starter

Taking in to account the high electrical load of a starter motor how will it be powered and what size battery would be fitted?..Ian

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Re: BSA M20 electric starter

My B33 fitted with a Pearson electric start uses a 12.5 amp battery. This fits into the place of the standard battery.

Re: BSA M20 electric starter

Hello Ian, Dimas.

I see that I did not upload the photos then...
I do not have photos now, but I will try to ask for it.

As mentioned, it is not me with this project, but a buddy.

I uploaded his clip demonstrating it:

The starter motor in located under the left footrest you can see in the clip.
If I am not mistaken, the starter is out of Honda magna 750, which he reversed the rotating direction,
and it connects directly to the crank via a directional coupler. (Like a ratchet action)

This is as much as I recall, but I will try to get more info.

He does not use the exhaust valve lifter when starting, (The bike has a good compression)
And the battery is 12V, 12 or 14 AH.


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Re: BSA M20 electric starter


Reading now,
I see that I pretty much repeated what I already said then, at the time I posted the thread...

OK, I will try to have photos and And any other details and post it.


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