For the 2023 season, a service is on the to-do list for the YB9 Bellaria. This fine machine is now a proud 30 years old and is set to receive an H-registration. Since its purchase, it has mostly been sitting around, and even back then, it never ran particularly well. A perfect opportunity for the full service program.
Anything beyond an oil change on the Bellaria requires the removal of the one-piece full fairing. Since I don’t have a rail above my lifting platform, I have to remove the fairing outside. For a stable setup, I place the Bimota on the paddock stand and, after removing the windscreen, suspend it from the upper triple clamp with two tension straps. Once the front wheel and fender are removed, the fairing can also be taken off with the fork tubes still installed, as long as they have enough clearance from the ground.
To change the spark plugs, measure compression, and adjust the valves, the radiator with fan and the two frame braces of the front engine mount must be removed. Additionally, the wiring harness above the engine has to come out, as the valve cover cannot be lifted otherwise.
The compression on all four cylinders is between 13.5 and 14 bar—a good value for 30,000 kilometers of mileage. Valve clearance is consistently within tolerance on all 16 valves. Mechanically, the engine is in excellent condition. The reason for the poor running becomes clear when looking at the spark plugs: they show everything from light brown to soot black. Time to tackle the carburetors.
Disassembly reveals no abnormalities – everything is impeccably clean and correctly assembled. That leaves the CO adjustment. With the 4-in-1 exhaust system, cylinder-specific adjustment using a CO tester is not possible. Adjusting via temperature measurement with an infrared thermometer on the headers is too inaccurate. I therefore decide to modify the headers with measurement ports, drilling a 6 mm hole in each header, welding an M8 nut onto it, and later sealing it with a screw and sealing ring. This allows for precise carburetor adjustment, and the Bellaria now runs smoothly and evenly, just as it should.
