Is a red-hot head-pipe on your 4-stroke dirt bike “Okay”? No. Is it “normal?” Yes. Is there a way to fix it? Yes, there’s more than one possible solution, although there is one that stands out the most. If the head-pipe is red, that means the engine is getting too hot and needs more cooling. You may not need any parts to fix this though; let me explain…
There are two ways a 4-stroke dirt bike “cools”. Both of them require riding the bike, so don’t think you can stop and wait to let it cool down. In fact, you want to do just the opposite. First of all, riding the bike gives it air-flow through the radiators (If it’s liquid-cooled), naturally. So if you’re standing still, the cooling system isn’t going to do a whole lot. This is the most common issue for beginning riders and trail riders that do tight single track. The more you stay moving the better.
The next possible solution is similar to the first, but in a different way. You now know that riding at higher speeds will reduce the chances of overheating because radiators need air-flow. Gas is the other cooling part. The more gas going through the cylinder head and combustion chamber, the more it will keep it cool, to an extent. Like before, if you’re sitting with the bike idling, it’s not getting enough gas to burn and keep cool, even if your Jetting Is Correct (although, lean jetting can also cause overheating problems). It’s not necessarily the entire engine that overheats from a lack of gas. It’s the valves that start to heat up and eventually burn out. If you’ve been around 4-stroke motocross bikes at all, you have probably heard the term “Burnt a valve.” Well, this is one of the main reasons why it happens. The valves just get too hot too many times, causing them to burn up the edge and lose all compression. It’s better than dropping a valve, but still can be a costly repair.
Properly Warming Up Your Dirt Bike is part of it, which is why I never let my four-strokes idle for very long when I first start them up. How do I know this, you ask? Well, I know of many people that have burnt valves more often than usual, and it wasn’t coincidence. No, it was because they putt around on their bikes.
Not only does riding your bike harder and faster give it more air to cool it down, but it also gives it more gas to keep the valves cool, increasing longevity. You will also have more fun riding faster because you’re passing your buddies that are cruising along. All in all, a four-stroke motocross bike is made for one thing; to be raced, and raced to its potential. You don’t have to out-ride yourself, and I suggest you don’t. But, the more speed you can get, the better off your dirt bike will be. Quite the contrast compared to most other things, huh?
If your bike is overheating on a regular basis, you probably have bigger problems. Check out my article on Why Is My 4-Stroke Getting So Hot to see if any of those solutions can fix it. Good luck, and ride safe!