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Troubleshooting - Dirt/Pit Bike Will Only Run With Choke On

Is your dirt/pit bike or ATV only running when the choke is on?

You’re not alone.

It's a common problem, and there are a few potential causes.

Here are a few things to check:

Why a Dirt/Pit Bike or ATV Only Runs on Choke

Whether you have a 2-stroke or 4-stroke, dirt bikes and ATVs are designed to run a little leaner than your average street bike or car.

This is done for a few reasons:

1) To reduce emissions.

2) To prevent “pinging” or “knocking” (pre-ignition), which can damage the engine.

3) To improve gas mileage.

If your bike is only running with the choke on, it’s probably because it’s running too lean.

This can be caused by a few different things:

All internal combustion engines need three things to run: fuel, air, and spark. If any of these are missing or not working properly, the engine won’t run.

A dirt bike or ATV that only runs with the choke on is usually lacking one of these three things. Let’s take a look at each one.

Fuel

If your dirt bike or ATV only runs on a choke, it could be that the fuel isn’t getting to the engine.

This could be caused by a number of things, including:

  • A clogged fuel filter.
  • A clogged fuel line.
  • A faulty fuel pump.

If you suspect that the problem is with the fuel, the first thing you should do is check the fuel filter. If it’s clogged, replace it.

If that doesn't work, inspect the fuel line for clogs. If it's blocked, clear it out or replace it.

Finally, if neither of those solutions works, the problem is likely with the fuel pump. You’ll need to take it to a mechanic or replace it yourself.

Air

Another possible reason why your dirt bike or ATV only runs on a choke is that there isn’t enough air getting to the engine.

This could be caused by a number of things, including:

  • A dirty air filter.
  • A clogged air intake.
  • A faulty carburetor.

If you suspect an air problem, the first thing you should check is the air filter. If it's dusty, dirty, or needs to be replaced, do so.

If that doesn't work, look at the air intake. If it's blocked, clean it out.

Finally, if neither of those solutions works, the problem is likely with the carburetor.

You’ll need to take it to a mechanic or replace it yourself.

Spark

If your dirt bike or ATV only runs on a choke, it could also be that the spark isn’t working properly.

This could be caused by a number of things, including:

  • A dirty spark plug.
  • A faulty ignition coil.
  • A loose connection in the spark plug wire.

If you suspect that the problem is with the spark, the first thing you should do is check the spark plug. If it’s dirty, replace it or clean it.

If that doesn’t solve the problem, check the ignition coil. If it’s faulty, replace it.

Finally, if neither of those solutions works, the problem is likely with the spark plug wire.

Check the connection and make sure it’s tight.

Why a Motorcycle or ATV Engine Runs Too Lean

Why is the engine running too lean suddenly if you haven't adjusted the mixture screw on your carburetor?

The jets might be clogged, in which case you'll need to clean the carburetor, or there may be a leak allowing extra air into the carburetor.

Check the carburetor bowl gasket and the intake manifold gasket to see if they are leaking.

If neither of those is the problem, then you might need to rejet the carburetor.

This is a job for a mechanic unless you're familiar with carburetors and feel confident working on them.

The last thing to check is the air filter. If it's clogged, it will restrict the airflow into the engine, making it run leaner.

Clean or replace the air filter if necessary.

Keeping the Carburetor in Good Condition

If you're going to be gone for an extended period of time, never leave your carburetors filled with petrol if the engine isn't going to be on for a while.

Before storage, set the petcock to OFF and let the engine run until all fuel has been used.

Another way to prepare your carburetor for storage is by draining it of any remaining fuel.

To do this, remove the drain screw from the bottom of the carb's float bowl.

FAQs

How do I know if my choke is open or closed on my motorbike?

Turn on the ignition of your motorbike. Look for a small knob on the side of the carburetor. If the knob is in the up position, then the choke is open. If the knob is in the down position, then the choke is closed.

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