The manual for my TS (which has the same motor) says "In practice, therefore, one determines by experiment what opening of the valve is best suited to his engine".
It then goes on later to say "Generally speaking this valve should be opened only so far as will allow the pump to empty itself every eight or nine miles. This will suit moderate speed from 25 to 30 miles per hour. If higher speeds are indulged in, the valve should be set to allow the pump to empty oftener, say, every five miles"
In practice I use about a drip every 2 seconds
