RE: Picked up some old stuff. Questions.....
the fs 90 used the same valve lash clearance as the newer fs91 which was .004 to .010 both valves cold. I always favored the exhaust valve with a setting on the high side of the spec.[.008-.010]It didn't make much differemce on the larger engines but I found this to be helpful on smaller ones[.52 or less] I have a .52 that wouldn't run once under load [would falter and slow dowm and most times stop after a couple of mimutes in the air]and was just about to abandon it when I discovered that the exhaust valve needed a little more clearance when hot and set the lash at .009 where upon it ran like a champ