Hello,
I have used my 2012 as my main transport since purchasing it a couple years ago. It is a fantastic bike for my purposes. I have had a long standing love affair with 250cc bikes starting with my first YZ 250 F for motocross a decade ago. So heres some suggestions for the most fun mods that DO deliver a noticeable increase on this bike when in the mid range speeds and around town or in corners.
I put on a stainless header and a two brothers carbon fiber black exhaust. it looks sharp, is extremely throaty and appealing in sound (turns a lot of heads and is distinctive), gives a better throttle response (maybe 1 or 2 HP) and most importantly saves a ton of weight from the bulky stock exhaust.
Adding a K&N air filter is not so expensive and improves the breathing further with the exhaust.
The stock tires are fine but better rubber (pirelli diablo rosso IIs or whatever) make handling nicer even.
A 13T sprocket up front lowers top end to around 85mph instead of 90 but is fun in corners and i have no need of 90mph out of this bike.
a power commander is pretty insignificant to me as the bike really runs great with the exhaust and filter. The more weight you shed the better if you don't have a passenger you could go with changing pegs and things. but for a regular rider its nice to have the passenger set up. I even bolted a rack on mine and an egg crate so i can carry gear as well as a passenger, even a dog at times. all in all you can get maybe a total of 3 to 5 more hp with basic mods. more importantly is losing weight if you are going that direction. but the bike is great fun and well set up. its all about appeal in riding to me.
maintain it well and you will get years of fun use.
ride safe and enjoy lifes turns.

Facts:
1. On a stock CBR250R the power and torque drop off quickly past 8000rpm. That gives another 2500 safe engine rpms that aren't worth using.

2. Honda know how to get 40hp out of a street legal 250 cylinder. They put four of them side by side and call the result a Fireblade.

3. The NX250 I had ten years ago did pull evenly through to 10000rpm although I doubt it had as high peak torque as the CBR250R.

Googling power curves for the CBR250 shows that Honda have made the motor quite peaky by four stroke single cylinder standards, with that peak occurring quite early. What I think most folks here are looking for is not tarmac shredding power but a few more usable revs and less gear changing required to keep in the sweet spot. If that could be done for 10 to 20% the cost of the bike I'd go for it.

A Dynojet power commander 5 from www.jetttuning.com with modified gearing ticks all those boxes.

i think this is key. all i've taken off so far is the front fairings and stock headlight bracket (replaced w/ a yamaha fz16 headlight for a naked look).

the difference is noticeable; it definitely had a positive effect on the power profile and how the bike leans/turns.

i'm really looking forward to taking the stock exhaust off... should be an even more significant loss of weight.

I went with a Leo Vince evo II and a 40t rear Vortex sprocket. The bike accelerates harder and the throttle response is sharper. Cycle World got 3 more HP with this exhaust. The bike pulls harder and is a lot more fun. But it will always be a 250 single so I'm going to run it hard. From 7000 to 9500 on tight curvy roads it at least feels fast and makes me grin like a lunatic!

Any reason you went with a 40T rear instead of the (cheaper) 13T front?

Also, definitely* need a K&N air filter. *waits for bites*

*Stock air filter is more than sufficient.

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yeah going from stock to carbon on the muffler was HUGE

I'm in the middle of turning my 2012 CBR250R from a combined street/track bike into a full fledged track only racer. Here's a thread that shows pretty much everything you can do to improve the CBR250R. Not all will be applicable to you, since some is for track only, but this is a great thread!

https://www.cbr250.net/forum/cbr250-p...race-bike.html

As to whether you should improve this bike or not - that's completely personal. I love this bike because you ride 10/10 with almost no mods (on the track) from the start. However, now that I'm going to enter into races with it, I want to be able to beat the Ninjettes. To each their own... mod to your heart's content.

I have a two brothers exhaust and took my airfilter cover off, that really helped a lot.
Also a set of Pirelli Sport Demons, added 5 hp right there.

A guy in my group was boasting about trading in his Triumph Daytona to get a brand new BMW S1000...after a 3 corners he was no longer in my mirrors and I ended up waiting awhile at the end of the road.
Lesson to be taken: Learn to ride quickly and you won't need to do major mods (Unless your racing).

Not trying to revive this thread but come on, it’s a 250! It’s a starter/commuter bike! It’s far from a performance machinery gstting 70 mpg! Step up & get a different bike if you want thrills. I recently got my 250 cause it will keep me out of trouble so I can enjoy riding my S1000rr on my days off.