Ace has built her own go-kart, but when she is ready for a test run it will not start, and she has to figure out what part is missing--and then in the middle of the race something else goes wrong.
Ace gets her mountain bike ready for the big bike race, but during the race Ace's bike chain comes off the sprocket, and a tire goes flat--luckily she has her tools with her to fix the problem so she can finish the race.