I bought CBR250R MC41 when they 1st came out and sold to friend in town (picked up Ninja 250 for racing). He still has it and is actually considering racing it and keeping his CB500F as street bike
I've been racing Ninja 250 past 6-years with AFM, ASMA and CVMA. Have CBR250RR MC22 for street use and in process of building CBR250R MC19 for track with remaining parts. I used RaceTech's calculator and purchased their springs.
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My 1st year, I weighed 205-lbs and used their guide for 1.0kg/mm springs. I'm now 170-lbs and use 0.85kg/mm springs. Their calculator suggest 0.80kg/mm springs for you. Better to get slightly softer than too stiff. Otherwise, you'll end up skipping across tops of bumps and going wide around corners. Too stiff also overwhelms dampers and causes bounciness and pogo'ing. You'll want to replace fork-oil with higher weight to match higher spring-rate. Also good idea to get the Gold Valve Emulators, really smooths out front-end as it gives more precise control over damping.