You learn quickly that chain maintenance is a key factor with a mini sprint. You need to clean it after each race, not just keep dumping chain lube on it but actually clean it so it moves smoothly.

Also, chain does go bad....they stretch out, become weak. Lay an old chain on the ground next to a new one and try to bend it sideways. You can see the difference.

If your chain is an afterthought when it comes to car maintenance you are going to have problems.