I agree with Paul, it will be much simpler to replace those gear changers than try and modify them.
I prefer the more natural action and cleaner look of the twist throttle control:
![](http://www.arhservices.co.uk/GoldenMotor/Controls.JPG)
I just wish the grips were shorter, or at least went completely over the handlebar instead of sticking out an extra 25-30mm on each end.
![Huh ???](https://goldenmotor.com/SMF/Smileys/default/huh.gif)
But, if I was planning on using a thumb throttle, I would fit of a pair of these:
And a 11-30T 7 speed thread-on freewheel:
![](http://i.ebayimg.com/t/DNP-Epoch-7-Speed-Freewheel-11T-Small-Cog-11-30-/00/s/MjYyWDI4Mg==/$(KGrHqR,!pgFBYBm!81vBQhZIYB0CQ~~60_35.JPG)
The 30 tooth 1st gear sprocket is not likely to be used much
(if at all) but the 11 tooth 7th gear sprocket will be a necessity if you want your legs to be able to keep up with the pedals while the motor is running at full speed.
![Wink ;)](https://goldenmotor.com/SMF/Smileys/default/wink.gif)
Here's a handy little tip for anyone using the thumb throttle:
Find a couple of coins or washers which are the same diameter as the handlebars
(~22mm) and pop one inside each of the rubber grips before pushing the grips onto the handlebars. If your bike falls over, they should prevent the handlebars from punching a hole right through the end of the rubber grips as they hit the ground.
Alan