Plunger Gearbox

[Roadhog]

Quick question. What are the differences between a A7 and A10 Plunger Gearbox. As its difficult to know when buying a spare one for parts. Thanks . 

[Black Sheep]

To the best of my knowledge from 1951 on they were identical.

[duTch]

 

To the best of my knowledge from 1951 on they were identical.

  I know it's about the difference between A7 & A10, so that's probably technically correct-ish, but how does one determine a pre-'51 box which are *almost * the same ?
 The only way I know is the kick starter spring is different and therefore mounted different. This is obvious externally by the anchor peg nut just behind the kicker shaft on the outside- early ones don't have it.
 If it's a pre-'51 box, the gears will likely be different and can be swapped out as a set, but not individually interchangeable.

 No doubt someone will have better information

 Hiya Roadhog  , but yea better get over to the 'intro' board and spin a yarn or two before you're busted...

[JulianS]

The early boxes were fitted to the long stroke A7 and a small number of the first A10 in 1950. There were a number of changes in 1950 including the cover detailed by duTch - for example the selectors from early box are different to and cannt be fitted to later boxes.

The number ZA7 11192 after which changes happened, is, I think, the last of the long stroke A7 engines.

The useful book "BSA Twin Motor Cycles" includes a few details, and some engine and frame numbers, in the photos below. It also details the major change to later boxes when the sprocket oil seal was fitted in 1951.

The majority of plunger boxes will obviously be the later type but for peace of mind suggest viewing the early and later parts books and compare part numbers to eastablish any other differences.

[duTch]

 So,  to answer the original question;
 

...What are the differences between a A7 and A10 Plunger Gearbox. ...

 ...Nothing, same box- with consideration off/to above mentioned stuff 

[Roadhog]

Ok where is the "Intro Board" and why is this required. Im not that new. Thanks

[duTch]

 Sorry- I thought I read ' Posts 1 ' , must've seen the 'Karma 1' .....I must've missed previous posts- anyway I guess it must be this one if you really need to know;

 https://www.a7a10.net/forum/index.php?board=13.0