Re: pulled the string
I'm not exactly sure what those grips look like, but the ones on my Schwinn were flexible rubber. I rolled them off as though I was working in a prophylactic factory. For the grip shifter, I moved mine to the left side, seemed easier to get to. But I've seen pics of people who keep it on the right side, just in a little further. If you have front and rear grip shifters, just move them in to make room for the other stuff (the shifters should be the first things on the bars).
Once you have a motor on, you're not going to make a whole lot of use of those shifters anymore. I sometimes shift into a high gear to help the engine when I'm riding uphill or into the wind, but apart from that, it's 3rd gear all the time.
If you have a front shift, you might consider taking that whole thing off completely, and just run the pedal chain on one front sprocket.