classic motorcycle forum

A while ago i agreed to help a friend build a custom bike from an A10 BSA in boxes. He'd seen a chopper in the U.S that he liked and we were going to copy it loosely . I identified the forks and front hub as early 70's trail bike items ( sounds odd but neat looking ). It was suggested on a forum at the time that we change the bolted up rear hub for a neater riveted one and someone posted a link to one on ebay.I sent all the info to my friend and he bought it.
Two years later ( for various reasons ) he came round with the frame and wheels/forks etc. The idea was i'd dry build the back end to check clearance issues with the wider wheel laced onto the "new" hub.It was only when i was about to instal the wheel bearings that i noticed the thread for the bearing retainer is external , not internal like the old one. Any ideas what used these so i can find a retainer to fit?

Thanks for all the input so far...this is brilliant!  I wasn't sure a classic bike forum would be that keen on a special with an industrial motor. I have to say the idea of building a special from scratch is very refreshing.I have restored modern "classics" to stock, am about halfway through restoring a Bultaco Sherpa with a few subtle mods and building an HRC VF400RK TT F3 replica ( from genuine HRC manuals ) .The Bultaco is quite straight forward and i have a list of known parts it needs, the Honda is a bit more involved because it uses different forks and wheels and most of the special HRC race kit parts it needs will have to come from Japan ( which isn't easy or cheap ). So although i want a simple looking bike it might actually exercise the old grey matter a bit and require some engineering solutions along the way.I've seen similar projects on the web where the builder has made the frame, it would be nice to have it exactly how i want it but don't really know how hard it is to get one through the SVA test. I'm led to believe the bike test is quite a bit simpler than the car one...............more research

The inlet isn't very sporty, think that will get a straight one.I was surprised to see the pictures up because i couldn't preview them so thought they didn't upload.I managed to download the manual mentioned by john.k and had already bought a Howard engine manual (paper one) off ebay. hadn't undone anything yet so left-hand thread noted! Plenty of penetrating oil on it now,especially on the exhaust thread. I know everyone has their favorite penetrating oil or cocktail of solvent and oil to shift things but the best by far that i've come across is Kano Kroil . It's not cheap but it really does work.It was the only thing that managed to penetrate all the crud on a splined pto shaft that wouldn't move on a tractor mounted cement mixer so i could replace the chain.
I was at Newark autojumble on Sunday and had a look at a couple of girder forks and a few gearboxes. I have to confess to never having had a "British bike" on the road ( have had British framed Scrambler and have got British framed speedway bike ) so my knowledge of British bikes isn't as good as it should be but i have partially restored/recommissioned a '37 500 MSS Velo, rebuilt an Le Velo and building BSA A10 engine for a friends custom bike. So with your combined experience what sort of gearbox would be suitable? of all the pre-unit boxes i looked at  about half looked too small ( off lightweight Villiers etc ) some looked too chunky tho. It's not like it has massive HP but i'd like a neat "old looking" box with the primary on the correct side, also how many gears to be useable ?      Any ideas?

Thanks chaps for the quick replies. I do realise it's not a sporty engine, that was just what i got of the engine codes online.I have modern classics for sporty riding and just wanted something fun to build and to be able to collect random parts that look right at autojumbles. I will post pics when i've cleaned it a bit. Be warned, it is in pretty much "as found" condition" but it does turn over ( it was local and i didn't pay a lot for it ) .It is missing carb and mag, also the timing gear ( available 2nd hand online) and cover. It does have separate head so 1950?  Any idea what the last digit ( No 4 ) means? Not really bothered about age as it will still be more 30's style.Thanks all for the input.

Try contacting Hitchcocks motorcycles and ask them if they have any info or could point you in the right direction.They might have books/manuals etc. I was offered a competition Royal Enfield a couple of years ago  that i wasn't 100% sure was a genuine competition bike so i sent them an email and got a very helpful reply from the main man. Worth a try!