Is A Glowing Red Head Pipe Okay?

Is a red-hot glowing 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…

Head Pipe Glowing Red Hot

Ride It

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.

Gas Cools It

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 may be correct (although, lean jetting can also cause overheating problems).

A lower-performance trail bike should not have a glowing head pipe from idling. If that is the case, then the jetting is too lean, or the EFI is too lean and needs to be richer. This can be done with a bigger pilot jet for a carburetor, or richening the EFI system with a fuel programmer.

Valves Wear Quicker With Heat

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.

-Tom Stark

5 Responses

  1. Matt Dailey says:

    very helpfull

  2. Dan says:

    So I’ve checked the Jet settings, fuel screw rotations tested, fluids are ALL new, filter too, but I start the bike and still get a cherry pipe in 20 seconds.

  3. Shaun says:

    I’ve got a 2019 yz 85 and today i just got done riding I noticed the head pipe was glowing red like it was super hot is this normal and should I be worried about anything?

  4. Eben Grobbelaar says:

    I had this problem on my 510 Husky last week, outlet bend on the exhaust getting red hot within 2 minutes, bike not running smooth, requires choke to keep running, fuel running from carburator overflow. Thought sticky valve problem but found o-ring on seat of carburator float needle and seat failed and fuel bypassing seat, running free fuel to engine, causes rich fuel mix and after-burning in exhaust.
    PS if bike is running without airflow through radiator the whole engine will heat up and not only exhaust. Guess rich and lean mix problems can cause the exhaust heating. Hope this helps.

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