Hi all, I ride a 99 zx6r and have been hearing a strange noise lately. At idle, the engine sounds a bit rough but under acceleration sounds fine. HOWEVER, when I accelerate hard and back off to change gear for example, the engine makes a bit of a splutter noise kind of like when you blow a raspberry?? I recently had a major service done (24,000 km) and noticed valve clearances were not checked nor were carbies balanced. Maybe they weren't required?? Any advice appreciated. Cheers.