There is nothing like the feel of the open road flying by as you cruise down the highway on a motorcycle. Millions of bikers around the world not only love this sense of freedom, but also the fuel economy of motorcycles which are often double (sometimes triple) that of an automobile. However, despite the wallet-friendly fuel efficiency, there are signs and symptoms of problems for which gas-carbureted bike owners should watch out.
A common sign or symptom of a problem is when the bike is difficult to start when it's cold. This is often caused by a choke that isn't opening properly, resulting in a fuel mixture that isn't rich enough for a cold engine. If the choke isn't operating properly, you will notice that the fast idle needed to properly warm up the engine at first isn't present. This can result in the engine stalling until it finally reaches its normal operating temperature. Primary causes of this symptom are a dirty or damaged choke mechanism or choke linkage and can often be fixed with a new bimetal spring or a choke repair kit.
Difficulty starting when hot is another sign or symptom of a bad gas-carbuereted bike. With this symptom, the motorcycle refuses to turn over or may stall after starting, when the engine is already warm. This sign is usually not directly related to the carburetor. Instead, difficulty starting when hot often is due to excess heat near the carburetor, fuel pump or fuel lines. This results in the fuel boiling and vapor lock happens. Insulating fuel lines or moving them away from heat sources, such as the exhaust manifold, can fix this problem. Other causes may be a damaged starter or ignition module, or faulty battery connections.
Hesitation when accelerating is a sign that a gas-carbureted motorcycle has a problem. As the throttle is opened up, instead of increased power, the rider notices a sharp decrease in power as the engine stumbles before finally accelerating. This hesitation is usually a sign of a fuel mixture that is too lean and is often caused by a carburetor that is dirty or improperly adjusted. The carburetor, in this instance, may need to be either rebuilt or replaced. Cleaning the carburetor jets with a carburetor cleaner may also fix the problem. Additionally, the hesitation symptom may be indicative of a worn throttle shaft, a weak accelerator pump, a defective EGR valve, bad plug wires, dirty or worn spark plugs, weak ignition coil or an air leak somewhere else in the engine leaning out the fuel mixture.
Rough idling is another sign of a gas-carbureted motorcycle with a problem. This improper idling often is demonstrated as a stuttering or momentary galloping in the engine when the engine sits at idle, as opposed to the smooth, constant running it should display. Rough idling is typically a symptom of a lean misfire due to a fuel mixture that is too lean. A dirty or damaged carburetor may be the problem, leading to a need to clean, rebuild or replace the carburetor. Air leaks or an improperly functioning EGR valve may also be the source of the leaness, allowing too much air to enter the engine. Excessive blow-by, due to worn cylinders or rings, damaged valve seals or guides, dirty spark plugs, a weak coil or damaged plug wires may also be the root cause of this symptom.
