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MX - There is an air valve for each Moto, and this adjusts the amount of air going to the jet. The air is the 'kick' and adjusting it changes the feel of the jet or in the case of the Moto the speed. As you mentioned, there is a very narrow range of adjustment on the Motos.
Then there are the Diverter valves. These can be used to simply select which group of jets are on, but they can also be used to vary the water pressure in those jets. I have found that I can leave the air valve open for the Moto, and then back the water pressure off very slightly and get a more mellow Moto. But again, there is a very narrow margin of adjustability.
Thanks Chas. Actually this is a great segway into my next question (and it saves me from starting a new thread) So it is OK to position the diverter valve in between the 3 and 9 oclock positions?