Time to talk about one of the builds in the garage—the 2015 KTM RC390. This little Austrian single-cylinder is one of my favorite projects to date, and it perfectly captures the SPEC33 philosophy of taking a solid machine and transforming it into something truly unique through bold ideas and handcrafted engineering.
SPEC33 Build: 2015 KTM RC390
This bike is a perfect example of the SPEC33 method in action. Here’s a breakdown of the build:
The Foundation
The 2015 KTM RC390 is the perfect starting platform. It left the factory with a 373cc liquid-cooled single-cylinder engine producing around 44 horsepower and weighing just 324 pounds dry. It’s lightweight, agile, and built on KTM’s signature steel-trellis frame with WP suspension and Brembo brakes. The bike is race-ready from the start, but with its sharp looks and aggressive ergonomics, it practically begs for more.
The SPEC33 Transformation
This build is all about unlocking potential. For this KTM, I didn’t just add parts; I engineered a complete package. The heart of the build features a DynoJet ECU and custom injectors to dial in the fuel mapping perfectly, paired with a Competition Werkes USA exhaust that lets that single-cylinder breathe properly. On the chassis side, clip-ons and rearsets transform the riding position for a more aggressive stance, while the upgraded suspension (Ohlins or Andreani internals) provides the feedback you need to push harder.
Bold Choices & Real Mechanical Character
What makes this build special is attention to the details that other builders might ignore. A 1.8 Bar radiator cap and Spal fan keep temperatures in check during hard riding, addressing the RC390’s known cooling issues. I’ve also tweaked the final drive with 14/39 gearing for better acceleration out of corners, and on the braking side, upgraded pads and steel lines ensure you can stop as hard as you go.
This KTM isn’t just another bike—it’s a statement. Every weld, every adjustment, every part was chosen with intent. This is what SPEC33 is all about.
The KTM has been sold.