Scooter engine stops on quick throttle - idle fine!

If your scooter starts and idles fine, but dies when open the throttle, the following are some common reasons for such an issue.

You can easily solve this issue by following this step-by-step process.

Before we start - make sure that air filter is in good condition. Air filter is one of the main reason for this problem.

But scooter engine cutting off can be caused by any of the many reasons(related to ignition, fuel, air system related issues) listed below.

Air & vacuum related issues.

The first and easiest checks to do are related to air supply system.

Air filter.

The engine shuts off at the instant it stops getting air to breath. So a clean, new air filter is essential for smooth running.

Vacuum leak.

This is one of the most overlooked part of scooter repair. Tubes which are made of rubber/plastic expand when it is regularly exposed to heat near engine area.

Or tubes become stiff if the scooter is kept in storage without using, it will break-off when stretched, and it is not easy to spot leaks.

So make sure that all the tubes in the scooter are in the best condition and replace any that is not.

Ignition system related issues.

The most common ignition system issues, that cause, ‘‘the engine to shut down when accelerating’’ are as follows.

Spark plug.

Open the spark plug, inspect, repair or replace based on the condition of it.

Spark plug cap.

Sometimes spark plug cap is not tight/water damaged, and it will cause all sorts of problems. Make sure spark plug cap is in good condition and tightly put in place.

Ignition coil.

The chance of the ignition coil causing this particular issue is very low.

But as above-mentioned spark plug/spark plug issue, if the spark is not powerful enough, it can cause this issue.

Any other part of electrical system.

If you have a bright blue spark, that you can go on to the next step.

But as I mentioned above, any part of the electrical system can be a reason for this.

Fuel system issues.

Even more than the ignition system, fuel issues are more common. So the second step is to make sure there is no fuel related issues.

Carburetor - clean jets, tune, float.

It is relatively easy to open, clean and reinstall the carburetor.

Open everything clean all the jets, make sure float is not stuck.

Petcock valve.

Fuel from the tank goes to the carburetor via a petcock valve.

While one side of the petcock valve goes to carburetor to supply fuel, the other side goes to engine inlet area(vacuum line). A small amount of vacuum from the engine is enough to open the petcock valve.

If the petcock valve is faulty, fuel supply to the carburetor will be disturbed.

Auto/manual chock

Some scooters have auto/manual chock for cold start. Remove the wire going to the auto chock and make sure the manual chock is not engaged.

Other

It is not easy to pinpoint the issue when a scooter is acting up. It takes time and patience to figure out the exact issue or issues.

Even experienced mechanics fail, because they are busy, and move on to the next one without spending enough time on one motorcycle.

Engine oil.

This is an obvious requirement to for the engine to run. Make sure there is no leak & engine oil is in good condition.

Water in tank/carburetor.

Water inside the carburetor or inside the fuel tank will cause many issues similar. It is not easy to spot it, especially if water seeped into the fuel tank.