Vintage pre-war BSA B21 De-Luxe engine 250cc from 1939 – SOLD

Vintage pre-war BSA B21 De-Luxe engine 250cc from 1939 – SOLD



Gone to the Netherlands

Vintage pre-war BSA B21 De-Luxe engine, single cylinder OHV 250cc from 1939

What a lovely little 250cc prewar BSA engine. It’s mostly all there and is ideal for a project.

The engine number is clear and hasn’t been messed around with. I have shown the number in the images.

In my opinion, 1939 bikes are probably the pinnacle of the pre-war motorcycles. After that, things got very practical and aluminium was swapped out for iron wherever possible during WW2. Post war, designs changed to much sleeker machines.

This engine is for sale as a rebuild project. Overall, it’s in decent condition. The fins are good. The threads (That I can see) are decent. It has a piston attached to a a connecting rod and crank. The cases have matching numbers. So, at least, they were paired at factory in 1939. For the less observant, there is no barrel.

  • The piston has +036 stamped on the side and the conrod is numbered 65-444.
  • The engine number is shown in the images and dates the engine to 1939.
  • The crank moves with ease and the timing gears are installed, as shown.
  • From what I can see, you will need a barrel, piston rings, push rods and a few fastenings for the top cover on the rocker box.

I have no doubt that you will need to get other parts. These are generally available. If you are rebuilding a late 1930s BSA B21 Deluxe, or you are planning on building a fun project, then this little 250 could be the one.

Other prewar motorcycle parts: I have some. Please look through the items for sale or get in touch.




  • International shipping available. Please ask.
  • Combined shipping available if you buy other parts. 
  • I usually ship to most destinations. If you don’t see a price, please ask. Shipping is in addition to the listed price for the item.

Viewing: Please come and check it over before you buy. It is at PE28, near St Ives in Cambridgeshire.

Collection: If you don’t want it shipped, I have plenty of space. If you can’t collect for a while, it’s not a problem. However, I will need to be paid very soon after the sale. Thanks.

Payment: This site has a facility to pay online. Good old fashioned money on collection is preferred. I can accept payment through PayPal or by bank transfer as well.

Import Taxes: Please note that IMPORT DUTIES are not something I can control. If you are buying from outside the UK, there is a chance that you will have to pay import taxes. Import taxes vary from country to country. If there are charges to pay, it is the buyer’s responsibility to research the cost and pay the duties. The price that you see on my advert is for the item and not the item plus whatever taxes might be due.










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