Unfortunately, there is no suitable oversized piston for my 1937 Model 9 in the club shop. I therefore had a look around in Germany and found a company that manufactures bespoke forged pistons based on Mahle blanks, but also coats original pistons (depending on wear and tear).
https://wahl-spezialkolben.de/en/
I had the opportunity to visit the workshop and was impressed – not only by the workshop itself, but also by the friendly advice and expert knowledge regarding my Sunbeam. On a table lay dozens of folders containing drawings (partly hand-drawn) for various motorbike makes. Very impressive! The prices are also very attractive, ranging around 300 euros (which is significantly cheaper for me than a piston from the UK).
Cheers, Thomas