Hissing sid ?

[SURMANATOR]

My Gsa 58 plate has developed a hissing sort of noise from the engine sounds like radio static, came on riding back from France in a heavy rain storm
Had the annual service done at vines £124 +VAT No diff oil changed? Told them about the noise they put a rivit in the exhaust where the baffel would screw in (BOS end can) god knows why but they charged me £28 for the privilege Total bill £180 I think its coming from the alternator belt area any coments ?

 

[Kremmen]

If your of the opinion that the noise is coming from under the front cover, then i could, be something as simple as a slipping alternator belt or something more sinister like a seizing alternator bearing...
My first suggestion would be to remove the front cover to investigate, check the belt tension & then run her up and listen, see if the tone of the noise changes when the motor is revved....i know it's a silly comment to make, but please keep your fingers away from the belt & pulleys when the motor is running.