Re: any ideas how to make 1/5 turn throttle?
Back in 1973 I bought a DKW 125 to race District 37 Desert, Lightweight Division II. Like today it was generally thought that 1/4 turn throttle was probably optimal for dirt bikes. But that little "Deke" was such a screamer with an extremely narrow powerband that you never used half throttle - it was either full or off. What you really wanted was a toggle switch. Besides, less movement meant less fatigue on races like Barstow to Vegas that approached 200 miles in length.
The Deke had an odd 27mm Bing carb, and like all the German bikes came with really nice Magura hardware. So I went down to the local Maico dealership and bought a factory Magura throttle assembly from a Maico 400/501 that was made to pull a 46mm Bing slide up in a 1/4 turn.
That made the little 27mm slide lift from idle to full throttle in less than 1/8th of a turn. I had my toggle switch! Success!!
So if you really want a super-quick throttle, find a twist grip for a big, open-class dirt bike and you'll get your 1/6th turn or better for full throttle.