That's why I suggested motorcycle grips - they're all made like that, i.e. a larger internal diameter for the right hand grip (good pun, that!). A motorcycle throttle twist grip works in the same way as the Wisper pre-2009 one except of course it pulls a couple of cables rather than having a Hall effect sensor.I guess it might be, but thought I'd leave myself the option of putting the old ones back on in case the new didn't fitYou also might damage the throttle itself doing this. Oh, btw, be careful not to try to pull the wrog bit off, where the grip meets the part with the red button, there is what looks like a thin plastic disc that moves with the throttle - this is actually the end of the moulding underneath, and so stays on. Oh, yes, the other part is that the new grips are actualy two different sizes (slightly), and the bigger one is the thottle side.
I know not everyone on here has ridden motorbikes.
I suspect that if/when the new-style half-grip needs replacing you'll have a more obvious path, as this is similar in construction to the twist-shift gear controls on a mountain bike.
Rog.