khun grs25n

Hi All

I have the above but one with a problem . I have replaced the top large gear in the head of the turner and put some shim's in place and thought i had fixed it but then the rake head keeps knocking and will not turn . One arm was missing when I bought it I had purchased a new one and cam but as I went down the field it turned a couple of times then made a knocking sound so I parked it up at end of field and left it .ANY IDEAS PLEASE !!! before I get a disc cutter to it

Thanks Karch

khun grs25n