Pretty much every bike I have ever owned but then I would need huge a garage and many of the sales funded the next bike so they had to go.
But like most two stroke owners the one I regret selling most was my RD500YPVS, bought at the tender age of twenty after a Renault 5 made a right turn without 'seeing me' and bent my XJ600 rather badly.
It was used daily for two years and you can only imagine how it was ridden leaving everything in a four pipe cloud of two stroke smoke- every ride to work was like a GP (in my head).
Sold for £2200 losing me £300 on my purchase price so not too bad (my mate sold his one with a blown Stan Stevens stage three motor for £500)- I almost bought it back a couple of years ago, completely unrestored and looking every bit as lovely as when I sold it (except he'd had the wheels painted black instead of their original white) but £10k would have meant something else would have to go so I declined and let memories be memories.
