Make sure that you re-grease the front & especially the rear hubs, the headset & the bottom brackets on any bike you choose. You may need to remove the fenders or buy heavy duty ones if the ones on your bike are flimsy. (Most WallyWorld bikes have weak fenders). The fender issue is one of safety. The added vibrations from the engine can loosen mounting hardware or just cause the fenders themselves to sway. If one of those supports or the tip of a fender gets caught on a tire tread it can get sucked up into the bike frame and crumple up between the tire and the frame. Best case scenario is that your tire locks up at 25MPH and you manage to hold on for dear life and do not get hurt. Or your front wheels locks up, the bike stops & you continue over the bars at 25MPH.
Fortunately this has not happened to me because I have taken the advice of others on this forum, but sadly it has happened to people on this forum.
This is a quote that I like a lot. It applies here, and in almost every aspect of life:
"Anyone can learn from their own mistakes. Only a wise man can learn from the mistakes of others."
I am not always a wise man these days, and before the age of 38 I NEVER WAS.