Hmmm... Those pushrod tubes are quite distinctive, I'm thinking BSA B2 or B18. http://www.bsa1930s.nl/1936.htm
Thanks sb ... Looks to me like a B2 from the description on your link (compared with the B16 which had a single filler cap on the tank). "chrome plated petrol... Both oil and petrol filler caps in the petrol tank.." Two caps (oil & petrol) seen in chromed tank I think!