Stepping into an old thread I know, but the above is in error. Changing the chainring will affect the motor quite a lot. The issue is if you are climbing a steep hill and bogging the motor. A bigger ring will be a potential disaster in the making. As @tomjasz noted, the BBS01 and 02 are very sensitive to gearing, and this is because you can literally fry them if you bog them and subject them to load. Like going up a steep hill with a chubby rider and a load of groceries.I wouldn't worry about straining the motor, and changing the chainring won't really affect the motor much anyway. From the POV of the motor (so to speak) it's how fast you go up the hill, not how fast the chainring is turning that matters, at least over a much broader range of outputs than a human.
I typically use a 42T front chainring. Its the smallest possible that still gives you that steep offset. I recently built a bike that used the Lekkie 40T - but that needs a special motor cover to let the smaller ring fit and still have its steep offset. Not a thing for the beginner to tackle. My longtail Big Fat Dummy uses a 36T ring because it runs VERY steep hills ... but that longtail means a 215+ link chain which lets me lose the offset without losing my big gears in back... a special case. The 36T allows the motor to survive the punishment it gets. And my Bullitt cargo bike which lives only on flat land can take a 52T ring... but only because I run it 2-4 cogs in for straight chainline.
My Envoy runs in hill-strewn Monterey and I positively crawl up hills right now with its 42T ring (46T big cog in back), coming back from the store. I'm going to switch to a 40T (I can't lose my offset on this one) to ease the motor's life a bit, but of course thats a full weekend project since I have to do the main gear swap inside the new motor cover, then file down the nub on the motor casing, clean every bit of metal shaving off etc. etc. etc.