This is one these questions where you get a thousand different answers.
This is going to be the least common answer, and I'll probably get a lot of criticism about it.
I tracked my streetbike. For years.
I never got a dedicated trackbike.
I did between 6-12 track days a year depending on our travel schedule, but I couldn't bear the thought of having a bike that gets used so infrequently and just sitting in the corner of the garage when it wasn't on the track.
So I changed the street fairings to a pair of cheap Chinesium plastics which served as my track fairings and kept those on full-time. When I wanted to ride street, I just put the nose cone and lights, indicators, mirrors and license plate bracket back on.
My rationale was that if you buy a modern sportbike, it already comes stock with all the parts needed for track: suspension, high rearsets, steering damper. All the guys saying you should change the suspension out, my question was, "Am I really that good that I will be *that* much faster than what comes stock on a supersport or superbike? Some models of which are already homologated for top-tier racing?"
The answer, obviously, was no. So I got a sportbike and I tracked it as is. No aftermarket anything except maybe for a set of Woodcraft pegs because those were knurled and my boots kept slipping off the stock pegs. Also adjustable, so I could raise the rearsets for my short-azz legs.
When you get so good that stock suspension becomes the critical limiting factor and you are chasing milliseconds, not whole seconds off your laptimes, then you can always change out the suspension later. Race suspension is still street-legal on a streetbike.
Pros:
- You get to ride the same bike on the street and on the track. It's in use all the time.
- You get used to the bike's ergos, the way it handles, accelerates, stops all the time, not just a handful of times a year.
Cons:
- If you crash the bike, you can't ride street until you fix it
- If you buy a nice bike, you will ugly-cry large rivers of man-tears if you crash
- The biggest con is that you will never push past your comfort zone on your streetbike because it's your only ride. You will likely learn a lot faster on a cheap-o track-only motorcycle that you're not worried about tossing down the track.
- The good suspension, brakes and kit probably only applies to 600cc and 1000cc sportbikes. A lot of the lower displacement bikes probably won't have quality components.
- If you are far outside the spec of what the manufacturers build most bikes for, which is about ~175lbs, then you might need to modify the suspension and ergos anyway to fit your body size and weight
Anyway, just a different answer from what's already been written.
Not everyone who rides track regularly owns a dedicated track bike.