On most BSA's the frame number is located in the following places. It is always stamped; raised numbers are casting part numbers.
Up until it is rare for the engine and frame number to be identical and where the frame is shared by several models the codes start with the smallest model e. This varies from model to Bsa m20 dating but usually it is on the front top frame member either the front seat stay or by the steering head. On the front down tube below or in front of the petrol tank. The exception is the early Bantams where the frame number is between the front engine mounting plate.
These are usually faint and small.
By the steering head reinforcing plate or front down tube. Some Bantams on the engine mounting plate, these sometimes break and re- welding obliterates the
Bsa m20 dating. Front engine mounting lug but the engine and frame numbers are the same.
The oil in frame B- series are stamped on the prop stand Bsa m20 dating. Engine numbers Bsa m20 dating easier to find usually by the crankcase mouth on the primary side.
Exceptions are the Bantams which could be stamped on the front mounting point or just behind the crankcase mouth. This is just a guide and will fit most situations but frames were legitimately re- stamped by dealers if the original was damaged and a replacement fitted. These could be stamped anywhere and often were
Bsa m20 dating stamped at all!
Identifying engine and frame numbers, season onwards. Owners with late model BSA's can easily identify the month and year of their machine as the factory adopted a dating system for frame and engine numbers for the season models. As with all previous BSA seasons the model year started after the factory shutdown in July so that models were those made from Augustthrough to July They would however have some machines in stock so that so that it is possible that a July model may be to either the previous or the next year's specification.
Bsa m20 dating consisted of three parts, the first as two letters giving month and year respectively, the second was a five digit number and the third a model code. The engine and frame received the same markings. After dating and "Bsa m20 dating" many thousands of BSA's we "Bsa m20 dating" found that often a bike was built or shipped outside the dates given by the lettering system so this should only be used as a rough guide to the Bsa m20 dating and month of your machine.
The numbering started at the beginning of each season and always started at leaving the first 99 for experimental use.
The numbers were consecutively allocated throughout a model range so as an example all B group machines were lumped together irrespective of whether they were a B25 or B Sometimes they were despatched months earlier or later so the lettering system should just be taken "Bsa m20 dating" a rough guide.
The model designations are as follows. The years given are all model years: Rocket Three five speed - A75RV, and A75V - and Royal Star A50R - through to Thunderbolt A65T - through all years. Police Special A65P - through all years.
Lightning A65L - through all years. Firebird - and Lightning A70L Note in the frames for the twins were marked A65 with no model designation, from XG.
B Series This is a bit complicated! Starfire B25S - Sept to Gold Star - B25SS Victor Bsa m20 dating B25T Also this carried through to some but not all of the engines. After frame the engine and frame markings were the same.
There was a short period where the engine marking matched the frame marking but the frame prefix was A50; Presumably to use up stock in store prior to the changeover. Machines still in stock in the season about were resold in the and season. These returned machines are shown with a cross at the beginning of the despatch book record; they then reappear at the end of the book with the revised despatch date.
The models are identified by the adding of an "Bsa m20 dating" 0 at the end of the frame marking putting the number series into the ,'s. Machines re- exported in were stamped with a 'Y' suffix to indicate that they were models and therefore eligible for increased warranty. Click on the relevant year below for a complete listing of all engine and frame numbers: These lists have been compiled from numbers listed in the parts books from until the factory closed in and from known bikes up until Bsa m20 dating list was compiled painstakingly "Bsa m20 dating" the club's Librarian Steven Foden.
If you know of any discrepancies please email us. Engine and Frame Number Introduction Identifying your machine. Engine markings Engine numbers are easier to find usually by the crankcase mouth on the primary side. The date letters are as follows: The BSA W.D. M20 website. MPB, Forum, BSA dating service, Frame numbers, BSA tank numbers, BSA DVDs, Technical-section, Historic-info.
The bulk of the numbers given are for postwar machines, but those applying Bsa m20 dating the wartime M20 are included. These machines were built with matching engine. BSA used a system of letters and numbers for yearly identification of their machines.
M20 ESTIMATED, WM20,WM20, ,