Technical Advice

Why is my moped hard to start in the winter?

For a gasoline engine to start when it is cold, the carburetor must give the engine more fuel than normally needed to run when we all warmed up. This extra fuel is provided by the choke. So...


For a gasoline engine to start when it is cold, the carburetor must give the engine more fuel than normally needed to run when we all warmed up. This extra fuel is provided by the choke.

Some engines have a choke knob or lever that you operate, and some are automatic. Either way, the problem is that mopeds are designed to operate in the warm weather, and use the smallest amount of fuel possible.

For an engine to start in the winter, like a snowblower or snowmobile for example, the choke must add a significant amount of extra fuel, and the regular running circuit must also use more fuel. This is because the cold air is denser than the warm air, and to get the proper ratio or air to fuel more fuel is needed.

So, to make a moped start and run well in colder weather, you need to adjust the carburetor to make it richer. Most mopeds do not allow this type of adjustment, as it affects the amount of pollutants expelled. If the carburetor is adjusted by changing settings or jet size, then the moped will run poorly in the warmer weather unless changed back again.

Another problem is the quality of the fuel now sold at the gas pumps. Gasoline quality has noticeably declined over the last several years, and this is greatly affecting the ability to start in colder weather. The poor fuel also gums up the holes inside the carburetor, making them smaller, so even less fuel gets into the engine.

We end up with a carburetor that is not giving enough fuel, fuel that does not burn well, poor quality fuel that plugs the carburetor, and automatic chokes that do not choke enough. This is a concern for all mopeds, the better quality ones handing the problem better than cheap ones.

How can we get around this? Buy regular gas at a high volume gas station so you know you are getting fresh fuel, that helps. Not many people are using premium, so it seems to be rotting in the tank at the gas station. Make sure your carburetor is clean inside, and the air filter is all attached. Know how to operate your machine. Most choke units will not operate if you turn the throttle on the moped. So when you are trying to start it cold, do not turn the throttle unless the engine starts to run.