Why Does a Motorcycle Only Run with a Choke On? (2024)

FAQs

Why Does a Motorcycle Only Run with a Choke On? ›

A motorcycle will only run with a choke if dirt is trapped in the carburetor parts, including the petco*ck, pilot jets, fuel filters, and fuel lines. The dirt blocks the fuel channels, preventing the fuel-air mixture from reaching the carburetor.

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.

An engine that requires the choking (partial or full) after initial engine warm up is an indication that the engine fuel air mixture system is out of adjustment. Leaving the choke on while operating will result in excessive fuel consumption, irregular engine power performance and eventually may even damage the engine.

If a motorcycle or ATV only runs with the choke on, it's because the richer “choke on” mixture is actually closer to the engine's normal operating fuel mixture than the leaner “choke off” mixture. So when the choke is turned off, the engine gets too little fuel and too much air for it to run and it stalls.

With the choke on, the fuel blasts its way in and provides the carburetor with the fuel it needs. While this is relatively safe and doesn't harm any of the internal parts of the bike, it does lead to higher consumption of fuel.

If you forget to turn off the choke after starting the engine, it will continue to run rich, meaning there will be more fuel and less air. This can result in the engine operating inefficiently, consuming more fuel than necessary, producing excessive exhaust emissions, and even causing the spark plugs to foul.

The choke should be closed immediately after the engine starts running. If you leave it open, it can flood your engine with excess fuel, resulting in increased fuel consumption and reduced efficiency. Moreover, it can also damage the spark plugs.

Many times it's tiny pieces of fuel line clogging up the carburetor. There are several things inside the carb that can be causing this, a clogged air circuit, clogged fuel nozzle, incorrect float level, insufficient fuel reaching the carb.

When an engine starts, it needs a rich fuel-to-air mixture. Chokes are designed to close off or "choke" the air supply in order to provide the proper ratio of fuel to air. An engine needs more air as it warms up, so the choke needs to open to allow more air.

Check the choke valve and see if it is closing fully in the carb throat when you close the choke lever. There should be a limit screw or something to prevent a full closure. You might have to adjust the maximum throw of the choke cable to keep this from happening. The engine has to have some air to work.

Can you clean a small engine carburetor without removing it? ›

Use carburetor cleaner to remove deposits, clogs & debris

Deposits inside the carburetor can clog fuel and air passages and reduce performance or stop the engine altogether. Luckily, you can take care of many of these problems quickly and easily; often without even removing the carburetor from the engine.

The engine running with the choke on is a tell tall sign of the carb still having a blockage.

A motorcycle will only run with a choke if dirt is trapped in the carburetor parts, including the petco*ck, pilot jets, fuel filters, and fuel lines. The dirt blocks the fuel channels, preventing the fuel-air mixture from reaching the carburetor.

The purpose of the choke is to deliver an enriched air-fuel mixture into the cold engine to help it start. Having a rich air to fuel ratio flowing into the cold engine helps it start when cold. By having more fuel flowing into the cylinder, there is a higher chance of ignition.

How Long Should You Let a Motorcycle Warm Up? The amount of time can vary depending on factors like 1) temperature, 2) engine type, and 3) manufacturer recommendations. As a general guideline, let it idle for a few minutes, (1-3 minutes) or when it is very cold, a bit longer (3 -5 minutes).

An engine that will fire and run with the choke closed but dies when the choke is opened likely has debris at least partially blocking the fuel passages in the carburetor. In this condition the closed choke provides enough extra fuel to enter the engine to overcome the lack of fuel flowing through the other passages.

If your bike is dying when the "choke" is on, then it doesn't like the richened mixture. Even when warm, a richened mix shouldn't kill the engine, at worst it should just chug a bit. I'd start by inspecting/changing the plugs. Fouled plugs with weak spark don't tolerate much combustion activity.

The problem of having an engine “sputter” is typically caused by a fuel system issue. For pit bikes with smaller cc displacement engines, in order for a cylinder to fire efficiently, three separate components must work together; the fuel delivery system (carburetor), the ignition coil and wires and the spark plug.