A few years ago I had a Suzuki C-50. One of the Suzuki forum members came up with a way to adjust the valves without having to use feeler gauges. This made valve adjustments MUCH simplier and quicker! He calculated the degrees of rotation the screw would need to be turned out from where it first makes contact with the valve.
Here's how it worked:
.75mm pitch = .02952756" per revolution = .000082" per degree
intake .003" to .005" = 36-60 degrees (call it 45)
exhaust .007" to .009" = 85-109 degrees (call it 90)
So, to achieve the clearance for the intake valve, loosen the lock nut, screw the tappet down until it touches the top of the valve, and then back it off 45 degrees (1/8 turn) Same thing for the exhaust, back off 90 degrees (1/4 turn).
Does anyone know what the thread pitch on the TW's valve tappet screw is?