After replacing the belt on your upright bike, it is essential to test and adjust the bike to ensure that everything is working correctly. Start by taking the bike for a short ride to test the new belt's grip and performance. If you notice any slipping or grinding noises, adjust the tension of the belt using the belt tension gauge. You may also need to adjust other parts of the bike, such as the derailleur or brakes, to ensure that everything is working correctly.