Weird noise

[mike the bike]

My VT has started making an intermittent squeal /graunching noise.  It's engine related,  doesn't happen when rolling downhill with the engine off.  Doesn't seem to be revs related though.  I'm thinking that the water pump is squealing its head off.  What are they like to repair, if it is repairable or not, or should I just buy a replacement.

[mike the bike]

It's not the water pump.  I replaced that and it's exactly the same.  Because of the intermittent nature of the fault, I was led to believe it was engine related.  I then found it is speed related;  it does it rolling down hill with the engine off. I was then thinking of the front wheel bearings, although the wheel spins OK.
I finally worked out what's going on.  It's the speedometer that's making the noise.  Definitely a new one on me. I'm just relieved it's nowt to do with the engine.