First off, I have the wife's 2018 Ninja 650. I she has explored moving into a 600 for TC when we get stuck in the rain while traveling. It is stock for sure, but modding it is expensive but fun for sure. Plus I have 16 yr old that may want to ride. So the 400 would fit in well Thanks Rich
2nd Gen SV650. - Excellent track platform with plenty of knowledge and support over the years - Still very competitive, especially in the novice class - Bike prices are inexpensive, can pick up a setup SS bike for $3k-$5k - Used parts are plentiful - Interchangeable GSXR parts
I had a similar decision to yours. I have a 2016 Ninja 650 and used that on track to start. I started to spend money to make make that a dedicated track bike but realized I was going to spend way too much money to get the bike where I wanted it to be. Just the suspension alone gets you close to the cost of the SV. There are also a limited amount of people running the ninja, so you would need to buy mostly new parts. I would sell the Ninja and keep an eye out for race built SV's for sale on the forums and FB groups. I bet you will not spend much extra money if at all.
Where to buy the Pantone 281c number plates? I have sv650 naked and looking for number plates and brackets