Started with a FS1E when I was 16 (1979), can't remember what year the bike was, possibly N reg?
Then a SL125 which had a Dixon Racing 140cc big bore kit (part of their 550 upgrade kit I think? (they still around in Godalming?) - brilliant mudplugger of a bike, with great balance. Used it for loads of trialling, green lanes and enduros until it expired.
Replaced with a brand new DT175MX (reg was JWV ???W iirc). Bought it from Leask in Crawley, and again used every day plus plenty of laning and enduros on that. Good ol' days on Weavers Down
Went onto pure enduro machines after that - a Sachs engined special, built by PBH motorcycles who were around Caterham or Coulsdon (somewhere in Sth London, anyway), so no more Jap for the time...
regards, Phil