Thank you. I'll double check the pulley system as you suggest. It does make sense, although it does occur from start-up.
As far as a loose part (suggestion #2) goes, 2 very strong springs are in place & the pivot for the variable speed pulley shows little sign of wear. The bearings of the var.spd pulley are new.
The 3rd possibility may be what I don't like to think about.
It's pouring rain up here at the moment & the forecast doesn't look good for the next few days, so it may be a while before I get back to you. Many thanks for your help. Regards Kamel
