Hi all I am new member. I have a farmtrim 435 (direct drive) now this week I started our annual hedge trimming all fine for two days then third day I engaged pto to start the head and it made like a spitting or spatting noise until head was running then when Revving up to speed made same noises and again noises when tackling the hedge almost like its slipping and I’m unsure where to look first any help gratefully recieved . Many thanks S.