| The choke is supposed to keep your engine running while it warms up to operating temperature, and as it's a process that is taking place every time you start the motorcycle from cold condition, it's rather annoying if the choke is giving you problems. So what are the most common choke problems on a motorcycle ? Like in the previous chapter, things depend on how air and fuel are mixed on your bike.
Carburettor engines. - Smaller and cheaper bikes often have a very simple air restrictor on the air intake side of the carburettor. It's a simple sliding valve that is minimizing the air flow to the carburettor and therebu makse the air/fuel ratio richer. This type of choke will usually not let the engine idle properly during warm up, and you will probably have to control the idle RPM by holding the throttle slightly open. But if the sliding choke valve is working, there is not a lot that can go wrong here.
- More complex carburettors will have a separate warm up circuit which will add more fuel through a choke jet, and will mostly have a way to lift the throttle valve slightly in order to raise the RPM's a bit. Common problems are clogged choke jet nozzle or a malfunction in the link arm that will lift the throttle valve.
On the carburettor bike, the choke function is often making the air/fuel ratio extremely rich, and it's a general recommendation to shut off the choke at the earliest possible point - even if it means that you will have to hold the throttle open at the twist grip to prevent the engine from stalling.
Fuel injected engines.
The choke function on fuel injected bikes is usually working well and will normally not give the user any trouble.
It is important to determine if the engine have a general stalling problem or an issue with the choke circuit. The stalling related issues are covered on this page, so only the issues related to the choke circuit will be dealt with here.
- Faulty water temperature sensor or oil temperature sensor. This is quite simple: the engine is using one of these two sensors to determine a cold engine condition, and if the sensor is telling the fuel injection ECU (Computer) that the engine is warm, the ECU will obviously not start the choke program to warm up the engine.
- Faulty or misadjusted TPS sensor. This one is a bit more tricky, but the ECU is doing its basic fuel injection calculations based on throttle position and RPM, and if it receives false information on the position of the throttle valve, it will make the air/fuel ratio wrong, og not be able to raise the RPM correctly
- User operated choke lever not working correctly (Only on early fuel injected motorcycles)
Bottom line is that choke problems on a fuel injected motorcycle is most likely to be caused by faulty electronics, so the days when you could clean a jet to solve the problem are gone.
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