CB690 – A KTM 690 engined CB550

CB690, a KTM 690-Powered Honda CB550 Special – Fully Documented Build
A unique opportunity to own a properly engineered, one-off custom: a Honda CB550 chassis reworked to house a modern KTM 690 powertrain.
This bike was built by a mechanical engineer and motorcycle mechanic, and has a full UK MSVA certificate. This is NOT a Q plate machine. Everything on this bike is sorted and correct. No cheesy fasteners or wiring, no rubbing parts, nothing is unfinished.
This is not a cosmetic café build. It is a ground-up integration project combining classic proportions with modern performance – a lightweight, high-torque machine with a completely different character to the original bike.
The concept was simple: retain the clean lines and riding position of the CB550, while delivering the performance, reliability, and immediacy of a contemporary single-cylinder engine. The result is a bike that feels far closer to a modern muscle bike in terms of response, but with a vintage aesthetic.
The build involved substantial chassis modification and fabrication work. The original engine mounts were removed and replaced with fully custom-designed mounting points to suit the KTM engine. Frame sections were reworked and reinforced where required, with all alignment carried out using proper jigging to ensure correct geometry and chain line.
The entire build is documented in detail on DoTheTon, covering the process from initial concept through fabrication and assembly. This provides full transparency on the engineering decisions, workmanship, and development of the bike. Please go to my YouTube channel (link in the listing) and check out the other videos of the bike in action and some detail shots.
https://www.dotheton.com/threads/project-cb690-ktm-690-engine-in-a-cb550f-frame.75152/
The bike is fully assembled and running. It has been built to be ridden, not just displayed, and presents well as both a functional machine and a unique custom. It was pictured in Classic Bike magazine December 2025 in the reader section!
I’d be more than happy to discuss the build and answer any questions you might have. The bike was a labour of love, and I’m only selling it because I enjoy building more than I enjoy riding. The price is POA for now, but for reference I stopped counting when I got to around 16k in parts, and there was 7 years labour. The odometer reads 22000 miles from the original donor bike, but this bike has seen less than 100 shakedown miles since completion.