So riding home the other night I noticed that when I downshift and let the clutch out at mid range revs it starts to make a slight grinding noise. I can let it out really slowly and it works fine but if I go a little faster it makes this noise, almost like its slipping and making an unhealthy noise. Its a 2011 model at 11.5k kms due for 12k service. I ride a lot of high way kays, if that could effect it. The only variable I can think of is that I filled it with 98 instead of the 95 I usually go with at a different station. But I dont see how that could cause it. Its only really downshifting too, not when im starting off when the clutch is actually slipping, its fine, and only happens when downshifting whilst the engine is getting to the revs its meant to be at. If I rev match then its fine. Checked the chain tension, all okay there. Any ideas?