This is a retuned version of the engine you’ll find in the current Yamaha FZ6, which in turn is an old-school Yamaha R6 lump. It gets a new cylinder head, softer-performance camshafts, reshaped inlet ports, new forged pistons and a one-piece crankcase and cylinder block. The motor breathes through a new fuel-injection system with smaller diameter (down 32mm from 36mm) throttle bodies and a neat underslung exhaust, featuring a three-way catalytic converter. A new clutch and gearshift design make changing gear smoother and easier than the Yamaha FZ6. All this fettling is designed to make the Yamaha XJ6 flexible and friendly to ride. Claimed power and torque is less than the FZ6 (by 20bhp and 2ftlb), but usefully delivered much lower down the rev-range (2000rpm and 1500rpm).
There’s less need to stir the six-speed gearbox to keep up with traffic than the FZ6, making town riding nice and easy. At very low speeds the throttle response is snatchy when getting on and off the gas, but as speeds increase and the engine is spinning more it’s less of a problem. Overall the motor is very smooth, friendly and has lots of power (77bhp) if you’re prepared to rev it; enough for decent wheelies.
Despite the fettling to make the engine gruntier, you can still feel its supersports DNA and it never really relaxes, it’s always busy, buzzing and you often find yourself searching for another gear when you’re already in sixth. It’s not as bad as the Yamaha FZ6’s motor and you soon get used to it, but more grunt and less revs would make the Yamaha XJ6 even better. As it is, the engine is still impressive and the new, smoother-action clutch and gearbox help the job along.