A2 bike for track

I've been looking at bikes to upgrade from my 125, but I'm not sure about which ones would be decent on track. I'm looking for something that doesn't need to be restricted so I can use the full power. I'm hoping to do a couple track days next year just to see how I like it before I get something properly track focused. So far I've seen the duke 390 which looks the best while being cheap and good for parts. Does anyone have any other recommendations? I'm happy to do work on the bike and I'd rather something a bit older. Cheers