I went through the trouble to drill a small hole in the handle bar for the throttle grip, then the cheap plastic nub just broke off during installation. So I popped the bubble wrap and just used the plastic to keep the throttle handle in one place. These kits do have some really cheap parts, but they are fun once they are installed.
You might as well just break that nub off and don't even bother drilling through the handlebars. Other cheap parts in my kit were the studs for the front motor mount, one was actually bent when I received it in the mail. And the big fat chain that comes with the kit is ridiculously large and rubs on the frame and the tire. I was missing the cdi, a critical part. I ruined my back wheel trying to take apart the coaster brake and putting it back together. I just couldn't get it back together because I couldn't remove the sprocket, which is kind of cheaply made anyway, in my opinion. The kits should come with a better alternative than drilling through the frame to mount the engine. For the price and fun of a completed motorized bike I can't really complain at all because I love my MB, but the parts are cheap.