Most unusual your inlet vale, sure it wasn't the exhaust valve? I see Robinson SL 21 re, 'exhaust valves' has been deleted. So whatever that pertained to must now be in the Maint Manual.
In the hotter areas valve guide clearances is something all engineers pay particular attention to. At 285 hours you may have been in front of the first called up valve guide inspection.
Did you mean Number 2 cylinder?
The engine cabinet temperatures are a scary thing in the R44 for sure.
I think it is an area that needs a lot more research work for the hot climes.
tet