I did take a file to the edges of an old belt and I wire wheeled the pulley groove. Where did you purchase the electric motor belt? Got a part number and or length?
I bought mine at Grainger. My belt length is likely different since my all my pulleys are mix and match. I would find the length of your present belt and use that. It was a Dayton 3L series belt with no cogs. I used a 3/8 belt instead of the 13/32 because that’s all they had.
Someone, maybe in another thread, suggested that the belts without cogs grip better. I haven’t found any auto belts with out cogs except at places like Year One, and they cost $40 or more before shipping.
If anyone knows where you can get auto belts without cogs, please let me know!