I made the following modifications to my 2012 KLX 250:
Installed a 300cc AHL cylinder made in China, replaced the airbox with a larger hole instead of an internal filter. Replaced the airbox connection with a throttle body connection from a 1990s KLX 300.
Removed the secondary valve in the throttle body.
Replaced the original 215cc injector with a 315cc one.
On the monoshock, I replaced the original spring with a Racetech suspension one, and installed a spacer inside to lower the rear shock by 3cm.
On the fork, I replaced the original springs with Racetech ones, and managed to lower the front by 2.5cm while maintaining the same travel and modifying the original parts.

I had the original ECU remapped by PIASINI ENGINEERING.
Attached are the torque-power graphs.
The torque and power values are at the wheel. To calculate them, 9% must be added to the engine.And we're at around 30 hp.
Voglio precisare che il grafico non è riferito alla mia KLX che risulta essere migliore.

 

Cool! Tell us more about remapping with piasini. I contacted them about a year ago, they told they can read and write klx250/300 ECU, but price for the hardware was steep.
Is this standard exhaust?

 

About two years ago, I was contacted by PIASINI ENGINEERING, but only this year did I manage to bring my KLX 250 with the 300 kit, on which I mounted a RAPID BIKE EVO additional control unit. It gave me good results, having autotuning for the map and accelerator pump adjustment, but it suffered from the summer heat, giving me problems with acceleration at low revs.
Piasini, having already remapped both a modified KLX 300 and a completely original KLX250 like that of a friend of mine, told me over the phone that if I wanted, I could simply send the two original control units, specifying which bike they were from, and they would reprogram them and return them by mail.
In agreement with my friend, we decided to go directly to Piasini. I can assure you it was a great experience; we met all the team members, both friendly and knowledgeable, and helpful.
At my request they took us to their offices and showed us the software and hardware they use to connect to the original control units, and also gave us explanations on how and what was modified. This is certainly not something that is easily found.We learned that the stock 215cc injector on the KLX250, which is only used at 80% capacity, has been increased to 100% of its capacity. On my KLX with a 300cc kit, I had already installed a 315cc injector; otherwise, the air-fuel mixture is too lean, making the bike unrideable and prone to dangerous detonations.
My KLX300 has improved even further; it's more responsive and seems to need a higher gear (driving at 70-85km/h, it delivers 30km/l). The stock KLX250 no longer has problems stalling at idle; the vacuum between 4,000 and 6,000 rpm has disappeared, and it has more punch.
My muffler isn't original; it no longer has a catalytic converter, but it's approved for noise. Basically, it's not fully open like a racing muffler. The manifold, however, has a diameter of 40mm and is homemade.

Reprogrammed stock KLX 250 graphic

 

This is a step in the right direction for sure. I still think I will want an editable solution to upgrade to the 351. I hope that 550 performance is able to do this.
Do I see that Piasini wants 1500 for the hardware to edit?
That's pretty steep.
What kind of market is there for a complete, 351 upgrade with injector and ECM?
How many kits will I have to sell to get my investment back?