CLEARANCES IN A VB CAM CHAMBER
Dear friends, I’d like your advice on a clearance problem in the cam chamber of my VB.
If I firmly secure the 5 set screws of the cover that goes over the cam and its followers something jams and holds the tappets up and the valves off their seats when I rotate the engine. However, if I back the set screws off by a quarter turn the jam is released allowing the tappets to drop and the valves to snap back on their seats. As the screws are quarter inch Whitworth and so 20tpi, a quarter turn must back the screws off by 12.5 thou. I assume that somehow the cam followers are being trapped on the cam follower pivot pin (part number 1475-29. Note I’d had 19.5 thou end float on the cam itself which I reduced with a 10 thou shim behind it.)
I noticed that the "gearcase to crankcase gasket" (part number 2030-55) that I’d fitted was 8 thou thick and that new ones from Draganfly are some 7 thou thicker at 15 thou so I fitted one – but the same thing happened with the tappets and valves hanging up. The next step is to fit two gaskets (with a thicker shim on the camshaft) and see what happens; do you think I’m on the right track? Has anyone else had this problem and if so what was the solution?
Thanks in advance, MikeN.