Thanks for the tip Tris . After a strip down and clean I have found all the saw needs is a main centre spring for the blade guard. It sort of works but is a bit unpredictable. Tried Rexon but the saw is too old for parts now. Tried a few of the usual after market parts suppliers, but no joy.
I was thinking maybe one from a newer model would fit, can't imagine that the design of a blade guard spring would need much design change from model to model.
Any ideas ?.