The coolant is pumped up from the water pump through that chromed pipe into the front top RHS corner of the upper crankcase, and it comes in around the cylinder sleeves/liners through those 3 holes at the (as we view it here below) bottom of the liner bores in the upper crankcase.
So if one were to use too much RTV silicone when fitting the liners, it can be pushed out and restrict the flow of coolant in around the associated sleeve.
Coolant then moves up through the head then and out through the thermostat/bypass on the LHS of the head, through the pipe to the top/lower RHS of the rad.