Dirt Bike Won’t Start Has Fuel & Spark

You want to ride but your dirt bike won’t start but it has fuel and spark. Those are just 2 parts to the equation, and just because you’re getting fuel and spark doesn’t mean it’s the right amount.

In this article, I’m going to show you the practical steps I take to get a dirt bike running when it won’t start and how to start diagnosing the problem.

2 stroke has fuel and spark but won’t start

Have you confirmed that it’s actually getting fuel to and through the engine? From the gas tank, through the fuel line, to the carb float bowl, and into the engine, it doesn’t take much to clog a passage.

May 13 Dirt Bike of the Month KTM 300EXC Dirt Bike Won't Start Has Fuel & Spark
A shiny bike is no good if you can’t start

Bike won’t start even with starting fluid

To confirm that it’s getting fuel, you can put a few drops or gas or starting fluid into the engine through the spark plug hole. If it still won’t start or make any kind of combustion noise, then you can confirm that it’s getting fuel but still not starting.

Spark

By taking the spark plug out but setting it on the engine with the plug cap installed you can test for spark. Slowly kick or turn the engine over (in the dark makes it easier to see) and you will see a small blue spark jump across the electrode/tip of the spark plug.

Air

So, you’ve confirmed that it’s getting fuel and spark but your dirt bike still won’t start. The only thing left is air. It’s more than likely not getting enough air to and through the engine.

A dirt bike that has fuel and spark but won’t start might be caused by:

  • A rag in the airbox
  • An air leak
  • A blown head gasket
  • A plugged/clogged exhaust
  • Low compression
Dirty Air Filter causes spark plug to foul
Dirty air filters can cause more problems than you think

While these aren’t the only reasons why your bike isn’t starting, these are the things that I would look into first.

Whether it’s a pit bike bike or full-sized dirt bike, 2 stroke or 4 stroke, they all operate on the same fundamentals.

You need the proper mixture of air, fuel and spark. To start and run properly, your dirt bike needs:

  • A clean and properly oiled air filter
  • A tightly sealed airbox/intake boot/carburetor
  • Jetting tuned for your specific bike, mods and climate
  • An engine with proper compression
  • The exhaust to be in good shape (relatively dent-free with proper seal and packing)

Did you change anything?

You also need to ask yourself if anything has changed since the last time you rode. Did this problem just start happening today? Did you do anything to your dirt bike, such as:

  • Remove the seat
  • Replace the air filter
  • Remove the gas tank
  • Change the exhaust

Any number of adjustments could’ve caused a change. Maybe you removed the tank and when re-installing it, an electrical connection got disconnected. Or you had a crash the last time you rode that broke the kill-switch.

Why does my dirt bike only start with starting fluid?

If you have to put starting fluid or a splash of gas into the cylinder to get it started, then the fueling system isn’t working properly. It’s not getting fuel to the engine, so you have to work your way down. 

If your dirt bike only starts with starting fluid, then check these:

  1. Clogged gas tank vent line (blow through it)
  2. Clogged petcock/filter in gas tank
  3. Clogged fuel line or inline fuel filter
  4. Dirty/clogged carburetor
  5. Low float level in carb
  6. Jetting is too lean

Dirt bike won’t start after sitting

Has your dirt bike been sitting for a few weeks, months, or even years? Pump gas these days is notorious for going bad very quickly. This means that if your dirt bike or pit bike ran before it sat, then the gas is bad and you probably need to drain and/or clean the carb and gas tank. 

Seals might be bad as well, but I wouldn’t replace anything until you know that it’s leaking. A proper carb cleaning requires you to take the carb off or your bike. Want a step by step guide on how I personally clean my dirt bike carbs without fail? Click here to learn more.

Kelley Fager

I help new riders learn how to safely ride and understand how to tune and fix your dirt bike in your garage.

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