I can send you pictures and measurements tonight. (Been off line due to surgery, but up & walking again)
last summer I sorted and organized the land O' forks and trees in storage. (Motorcycle hoarder).
BSA stuff gave me fits and massive confusion. Still have a few mystery parts, but I narrowed 98% of it down for years-makes-models.
Here is the quick version, be happy to post up a BSA Tree tech post for ID.
Based off the top of my head here is what I found:
BSA Preunit singles some years were narrower than the twins,. # part numbers pending
BSA Preunit twins there was some variables for compy models but most were pretty std (Lugs, steering locks, speedo/tach mount and taper for the forks
BSA Unit Singles are their own animal by them selves but are tell tale with a reverse pitch risers,
BSA unit twins. there is 3.5 variants. # part numbers pending. There is a variation similar to the Preunit twins but 2 versions of fork locks. There is an early casting number, a Dual part number, THEN there is the oddball 64-65 Mustache trees (pictured above in this discussion) These are harder to find and I am not clear what all the models they used them on. (Parts books sometimes show for all models, sometimes only certain ones like Hornet) Then Inexplicably they went back to the Preunit style trees again with a variation in fork locks. And finally was the head scratcher that took a lot of investigation. There was some mystery trees and what they are is somewhat resembling the preunit style but had small details different in their castings top and bottom trees. What I discovered is these are factory service replacement trees intended to be one size fits all for unit Twins.
Then ** Some fork parts interchanged with Triumphs for 68-70 with the 2LS brakes, and the noticable difference on the fork legs is the Fork oil seal holder/Spring abutment is LONGER on the BSA and Shorter for Triumph but the top trees differ between Triumph-BSA as well as wider to accomodate the 2LS brake after the first year. (late 67-early 68 trees are oddballs). Also, the brake actuator levers on the brakes differ between BSA-Triumph but the brake plate is the same for TLS.
OIF 1971-> Smaller stem and different spacing and does away with the BSA fork tube taper. Also steering locks
Triples- BSA & Triumph, look similar to the 68-70 trees but have tell tale tabs for brake lines.
OIF unit singles- These are alloy and similar but not exactly the same as Cerrani-Betors. The forks are the same but generally longer on scramblers, but same length on roadsters as OIF Twins. But the forks and trees were largely copied from Cerrani and similar forks. (Quite good actually if you switch to progressive springs)
**I spent HOURS accumulating part numbers and measuring, lots of study of many years parts books.
I also have a vintage bike magazine review-interview of early Rickmans with Bud & Dave Ekins of LA fame. They set up a lot of these (For McQueen and James Garner, as well as quite a few others) So they took BSA Trees, and modified them, cut the fork tube holes, machined out the tapers and welded on pinch bolts to allow the forks to be slid up or down into the trees to set up the bike for off road, the reason was in some cases a nose down attitude was helpful. Its also reprinted in a cycle world compilation. Ill post the dates, & if interest I can scan the article.
** As noted, the fork ears for units were a different length than Preunits, and some variations in that as well. Might be easier to just ALSO use the matching fork ears for the trees being used.
*** I am also matching trees up to projects (Triumph-BSA-Norton) and will be selling off extras soon.
In the interim, enjoy these pix of some Rickman bodywork pinstriped by the famous Von Dutch (Kenny Howard) who often was at Ekins shop. ( ** I have been exchanging emails with a former local club member who was a regular down at their shop and has some interesting pictures and stories)
