Best liter bike for track days??

If you’re used to a twin on the track, my recollection is that the biggest change when transitioning to an inline engine was how much easier and less chattery rev matching and engine braking is on the inline.

That said, a slipper clutch probably solves that for you.

But i’m In the “buy a clapped out 600 and ride it more, and leave it at the track if you bend anything significant in a crash.” I want my old F2 back.

 

Right! When did that happen, is it necessary?

Pfft. For a handful of trackdays per year, and trackdays only, all that's needed is a motor, two wheels and a seat. No matter your ride or your pace, you're gonna have the possibility of a trackday hero being your trackday zero.

750?
Why not?
I've tossed my '02 750 into the weeds plenty, I'm sure I've totaled it more than once. It's simple parts, readily found (for the most part) always starts and has even been neglected (put up wet) for about seven years. Recently (last year), I ensured the battery had a charge, added fresh fuel and vroom-vroom. Gave it a good going over and rode a couple dozen days last year.
Puttin' a new chain and sprockets on for this year and looking forward to another couple dozen days of riding.
Issues? The oil cooler weeps a little...an o-ring away from being a non-issue.

I understand the decision dilemna. No reason it can't be both.
I'd start with a seasoned, reasonably priced, competitively prepped package. Figure out your routine for the season, then ask yourself if a $4oK "risk" is necessary for the next season.

 

R1 CP4 at your service sire.