So the story goes Simon's released a set in 1982 and WP also had a pair for sale.
you have done your homework JI! yes there were early WP4054's back around 82, most likey only in europe and as prototype/test models/limited sets made before the production set came out on 84 KTM's No one can yet confirm exactly when they were available as aftermarket forks yet though.I have listing for WP4054 Non adjustable -revsion set #R601 1982-1988.
In my opinion, if you get a set of drum brake 4054's off a 84 KTM and then machine your own lower axle mount/cailiper carrier for your YZ with CR forks or what ever you want them for? then that would be perfectly legal because A) The forks are off a pre 85 model and B) the caliper carrier is custom made and not a off the shelf part from a later model as back in 84 someone could have done exactly the same thing and wanted 4054's on a yamaha or honda or what ever and got a set off a KTM and then decided they wanted a disc but from what i can gather there was no WP 4054 caliper carriers at all in pre 85 so they would have had to make their own. There is debate whether a 1985 or 1986 set of WP4054s are legal for pre 85 even if they are proven to be the same design internally and exteranlly as the 84 KTM forks even if you convert to drum brake or take off the 'factory built' 85 or 86 caliper carrier and built your own, so the only way i think you could safely do it with no arguments is to use a 84 KTM set of 4054's or one of those earlier limited production/prototype sets from europe the later which you would never find anyway.
There was a set of 'works' USD Ohlins forks on ebay this year, i dont think i saved the photos but there was some history behind them origiinating back to Belgium? The seller said they were 82 models however forum member Marc FX believed they were 85 model Ohlins USD forks and not 82 as the ebay listing said but he or the seller may not have been right or wrong.
