Stripped down the 4RT for a new cam chain etc. and had some starting problems which I thought I'd solved but after a couple of weeks it won't start again. I think I've got the tick over screw in the wrong place because it almost wants to start but won't quite. There is a big blue spark on the plug.  Where about should the tick over screw be set? On a carb they say "1 to 1 1/2 turns out" but what about the 4RT EFI.