large journal crank mains and big ends size

[asherjackson]

hi folks , ive a large journal crank and da10 crankcases from around 1962 the mains end measures  34.54mm or 1.3595 in
and big ends 4133mm or 1.6275 in

are these standard

[CheeserBeezer]

Std timing side journal is 1.3745 / 1.375. Big ends std are 1.6875 / 1.688, so your timing side is about 15 thou under and the big ends would appear to be 60 thou under. It may be that the big ends (if clean and tidy) could continue to be run without further attention. The timing side journal probably needs cleaning up and machining to fit a sloid lead bronze bush, unless this has already been done.

[limeyrob]

You need BSA Service Sheet 207, explains it all.
Its a free download and may be on this site or the BSAOC. Just do a search.
Print it off and take it to the machine shop.

[muskrat]

G'day Asher. 
https://www.a7a10.net/forum/index.php?topic=1475.0
https://www.bsawiki.co.uk/index.php?title=Chapter_list
You will find just about everything you need to know here.
Remember there is no such thing as a stupid question, may be a few silly answers!
The Forum has the best search system I've seen on many forums. Use it at will (I do).
Cheers

[Swarfcut]

   If the crank was from an assembled engine, then each big end shell should carry a stamped undersize on the back, and at 60 thou under, finding replacements could be a problem. If it was a purchase, sadly it has just scrap value, the cost of metal spraying and machining may prove prohibitive. Let's hope your micrometer is not telling the truth. Allowed ovality on the journals is 2 Thou max.

 In any event, clearing the sludge trap will be good practice for the next crank that comes along. Plenty on the Forum and YouTube to show how to do it. Poor oil flow to the big ends is the accepted cause of a failure shown below.

 Swarfy