Fresh Tires And Tire PressureIn the days leading up to the race, you may want to put completely new tires on the bike — front and rear. It's not always necessary if the current tires aren't worn down or lack any signs of deterioration, but generally it's good to start fresh. What are those signs? Missing or damaged knobs, knobs with rounded corners, some discoloration, and cracks throughout the tire. Many riders will ride their tires into the ground before changing them out for new ones. It's best to swap them out before they're a year old, not only for ideal performance but for safety as well. Whether the tires are swapped out or not, you should have a spare wheels set up and ready to go. It's better to have them and not need them, than need them and not have them. The uninitiated might not realize how big a role tire pressure plays in motocross. Sure, it's not nearly as important as other bike components, but it can give you a slight edge over other competitors. Different terrain calls for different tire pressure and when you find the right tire pressure, it becomes night and day. You may want lower pressure if you're riding on a sandy track. Meanwhile, when the track is more packed together, you'll want to increase the pressure. Always double check the air pressure on the day of the race to make sure it's where it should be.Replace The Air FilterCleaning is significantly more involved than simply washing the dirt bike. There are some components "under the hood," so to speak, you want to clean before a race or even replace. Start every race with a fresh air filter: If you enter a two-day race where you'll have to race two days in a row, it's recommended that you change out the air filter for a new one before the second day of racing. This is going keep your bike's performance in tip-top shape. While casual riders can wait a little longer to replace their air filter as long as they're cleaning it regularly, replacing it right before a race is going to ensure the bike runs smoothly. Once you have the new air filter, evenly apply filter oil to it before placing it in the bike. The oil is going to help the filter accomplish its job of catching contaminants. While you don't want to use too much oil, more is better than not enough.Possibly A Fresh Top EndAccording to Cody Tithof — former professional MX racer out of Perris, California — you want to "have a fresh top end put into the motor" in the days leading up to the race, but stresses that it's "only needed if the bike has too many hours on the current top end." There's not a lot of guesswork for experienced riders when figuring out if they need a new top end. If you know what to look out for, there are some signs that tell you it's time to have a look at the engine. One such sign is a lack of power. When you've been riding the same bike for a good amount of time, you know how it should feel when it's running optimally. So when you notice there's not as much "oomph" when you have the throttle pinned back, it's probably from the pistons being worn down. Also be aware of how many kicks it takes to start the bike. If it takes more than four kicks, there's likely something wrong with the top end. Different climates can have an effect on the time it takes to get a dirt bike started. More than a dozen attempts, and it's time to look at the engine's top end. Dirt bikes by nature are noisy machines, but there's a good noise and a bad noise. When it sounds like metal is clanking together or rattling, that's a bad noise and a sign that certain parts are worn out.