Pump governor

Firstly fantastic forum.. Right have a 5748 and have changed the oil in the pump. old stuff was just rust. But have since seen a post on here about running her with diesel in the pump. So have done this but she still won't quite idle. speeds up and drops off. On another post some one mentioned taking off the inspection cover and spraying with wd40. Is this inspection cover the diamond shaped bit held on with two bolts. Don't want to take it off and find springs and things jumping out and can I move things in there with a screw driver or is that going to damage or disturb some setting.. Also probably really stupid but rather than putting diesel in the pump can I put wd40 in and run for a few mins or is that total destruction imminent

Hi
putting WD40 innside will not hurt the mekaniks, but i am unserten how the old rubberseals will fer. The diamon shaped cover giv ackses to the govenor and the big rektangular one to the pump, thay can be taken of , and remember ther are two oilfils one for the pump and one for the govenor.
Bjarne