It was near the end of a 5-hour trail hammering and I had acquired "thumb pump syndrome"--a piddly phenomenon having the distinguishing characteristic of making your thumb unable/unwilling to apply more than a quarter throttle. Racers and recreational riders alike suffer from "thumb pump" and is more commonly found on long and rough rides. Your thumb muscles become so weak from overuse on a stiff throttle system that it's difficult to apply the throttle and even more difficult to apply it with any modulation. The above incident was the deciding factor in switching to a twist throttle even though my preference on an ATV is a thumb throttle.
The Product Normally you have two choices. Convert to a twist throttle or adjust the thumb throttle a little by spinning the housing on the bars and living with its shortcomings. Now there is another choice--an adjustable thumb throttle by Primal Speed Gear called The Nibby. This trick-looking piece of CNC-machined aluminum replaces your stock thumb lever allowing you to adjust its position anywhere from in front of the grip to behind the grip. The machined aluminum, rubber coated thumb area and high quality fasteners make it an attractive replacement.
Installation
Our ride testing consisted of twisty, rocky trails ridden aggressively and fast--the perfect environment for "thumb pump" to rear its ugly head. Sitting or standing, the throttle is equally comfortable and its position closer to the bars feels more natural and less fatiguing. The overall length of the lever is very close to the stock 250R part, so the travel and effort required remain about the same.