Hello,

I recently bought a Yamaha FZ16 and i've been riding 40km everyday to break it's engine in. The engine itself was extremely smooth. I changed the oil after 100km and continued the break-in process conscientiously. Only today, one week after the purchase and 404km on the odo, I tried to shift up without using the clutch. I revved smoothly from idling up, and slowly applied pressure on the shifter while revving. Now in theory, at a particular rpm, the shifter must softly give way and the next gear must smoothly click in. Only it wasn't so perfect in reality. A slightly louder than normal sound emanated from the gearbox (very slightly louder than normal) and the gear kicked in.

Ever since that, the engine seems to vibrate a bit when higher rpms are reached (just above 3000rpm in fact) as described:

1.) There is a particular rattlesnake sound about the engine which i'm pretty sure wasn't there before.

2.) There is a more disconcerting er... shall we say, "suffocated metallic" sound above 4000rpm; kind of like what it would have sounded if it had a k&n air filter with extra air intake adjustment installed, only much lower in volume. This sound is quite obnoxious, like as if (my imagination takes over) a piece of metal had disengaged from inside the gearbox, slipped in through the oil and gotten into the crank case.

What could possibly be the cause of these vibrations? Is it possible that a dog wheel got ground and that small pieces from the gearbox have entered the cylinder? I also seem to sense a lack of smoothness is delivery of power when i throttle from fully closed throttle (idle rpm) to the very next increment.

I would be extremely grateful for your opinions. Until some probable conclusion is reached, i'm keeping the bike in the shed.