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

Published: 30.8.22

Updated: 5.8.24

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.

Related: Why Does My Motorcycle Backfire?

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.

Related: How to Clean a Dirt Bike Air Filter

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.

Related: How Often Should You Change A Motorcycle Spark Plug?

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.

Related: Should You Run With The Choke Open Or Closed?

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.

Related: How to Kick Start a Dirt Bike (8 EASY STEPS)

Keeping the Carburetor in Good Condition

Proper carburetor maintenance is crucial for ensuring your dirt/pit bike runs smoothly and starts easily.

Here are some detailed tips to keep your carburetor in top shape:

Before Storage:

• If storing the bike for an extended period, never leave fuel in the carburetor. Set the petcock to OFF and let the engine run until all fuel has been used.

• Alternatively, drain the carburetor by removing the drain screw from the bottom of the float bowl. Collect the fuel in a suitable container for proper disposal.

• After draining, spray some carburetor cleaner into the fuel inlet and let it drain out to remove any residual fuel.

Regular Maintenance:

• Clean the carburetor every 6-12 months, depending on usage. More frequent cleaning may be necessary if the bike is used in dusty conditions.

• Use a quality carburetor cleaner spray to clean the exterior and accessible parts without disassembly.

• For a thorough cleaning, disassemble the carburetor and soak the parts in carburetor cleaner solution. Use a soft brush to gently remove deposits from jets and passages.

• Inspect and replace the float bowl gasket if it shows signs of wear or damage.

• Check and adjust the float level according to your bike's specifications to ensure proper fuel flow.

Preventive Measures:

• Use fresh, high-quality fuel and avoid leaving it in the tank for extended periods. Old fuel can lead to gum deposits in the carburetor.

• Consider using a fuel stabiliser if the bike will be stored for more than a month.

• Install an inline fuel filter between the tank and carburetor to catch any debris before it reaches the carb.

• Regularly clean or replace the air filter to prevent dirt from entering the carburetor.

By following these maintenance tips, you can significantly reduce the chances of carburetor-related issues and keep your dirt/pit bike running smoothly.

Remember, a well-maintained carburetor is key to optimal engine performance and easy starting.

Common Mistakes When Fixing Choke Issues

When troubleshooting choke-related problems on your dirt/pit bike, it's important to avoid these common mistakes:

Overlooking Simple Solutions:

• Many riders jump to complex fixes without checking basic issues first. Always start with the simplest explanations, such as a clogged air filter or stale fuel.
• Solution: Begin your troubleshooting with a visual inspection and basic maintenance checks before diving into more complex repairs.

Improper Carburetor Adjustment:

• Overzealous adjustments to the carburetor can worsen the problem. Incorrect air-fuel mixture settings can cause the bike to run poorly with or without the choke.
• Solution: Make small, incremental adjustments to the carburetor. If you're unsure, consult the bike's manual or seek professional help.

Ignoring Fuel Quality:

• Using old or low-quality fuel can cause starting issues that mimic choke problems. Stale gas can clog fuel lines and jets.
• Solution: Always use fresh, high-quality fuel and consider adding a fuel stabilizer if the bike will be stored for extended periods.

Neglecting Regular Maintenance:

• Skipping routine maintenance can lead to a build-up of issues that affect the choke system and overall engine performance.
• Solution: Stick to a regular maintenance schedule, including air filter cleaning, oil changes, and carburetor checks.

Misdiagnosing Electrical Issues:

• Sometimes, what appears to be a choke problem is actually an electrical issue, such as a faulty spark plug or ignition system.
• Solution: Don't rule out electrical components. Check spark plugs, ignition timing, and battery connections as part of your troubleshooting process.

Improper Choke Cable Adjustment:

• A poorly adjusted choke cable can prevent the choke from fully opening or closing, leading to starting and running issues.
• Solution: Regularly inspect and adjust the choke cable according to your bike's specifications.

Rushing the Warm-Up Process:

• Some riders mistake a normal warm-up period for a choke problem. Cold engines often need time to warm up before running smoothly without the choke.
• Solution: Allow adequate warm-up time, especially in colder weather, before concluding there's an issue with the choke system.

DIY Repairs Without Proper Knowledge:

• Attempting complex repairs without the necessary skills or tools can lead to further damage.
• Solution: Know your limits. If a problem persists after basic troubleshooting, consider seeking help from a qualified mechanic.

By avoiding these common mistakes, you can more effectively diagnose and resolve choke-related issues on your dirt/pit bike.

Remember, patience and a systematic approach are key to successful troubleshooting and maintenance.

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.