The 7 speed shimano rear axle common on discount store bikes tends to unscrew the race & drop the balls, somewhere above 4000 miles. They left out a lock nut to save $.12. Luckily I was only 4 miles from home when it happened, didn't have to call a tow truck. Check specs to see what this bike has. Also a SRAM shifter is more precise.
Lock nut is a 3/8"x26 tpi. Such nuts are listed on a website, but niagara twice shipped me something else instead. They are now thebikeshopstore.com . They refunded the money but didn't ship me a correct part. I ended up buying a $12 tap from victortools.net and making some. Meanwhile bought another flea market bike, since I don't have a car running.
Buy an 8 speed shimano sprocket rear axle, or a rear hub motor with an entirely different rear axle setup. The yubabikes bodaboda left has an 8 speed sprocket, and I put a front motor on it. I first installed a DD rear motor but the 7 speed sprocket cluster that came with it was only 14:28. I need 32 to get up hills around here unpowered, and I could only help the motor up to 11 mph with 14 small sprocket. 12:32 seven speed sprockets are listed on websites but no-one ever has one in stock. 8 speed were too wide. Front wheel drive is fine except on ice. I have battery mounted on front end for the weight.