My son has a yiben motro scooter model yb50qt-3 year 07 it starts then stalls i have checked the carb and its clean and also blown the fuel pipes but still happens can you help chris make and model not on here

If the old gas sat in the scooter for a long time the carburetor may be lacquered over and may need to be cleaned. If it has a manual choke see if adjusting that while running will allow it more RPM.

your carb mixing screw may be to ritch so anny air resticition ist going to notmix fuel and air right lean it out

1. Try depressing the brake handle when starting.
2. The battery has not been charged.
3. The battery is hooked up wrong. This is often the reason for blown fuses.
4. There isn't enough gas or two-stroke oil in the scooter.
5. There is a gas flow problem, especially on the Euro Scooter or Yamaha models.
6. The spark plug wire is not connected.
7. A low battery or bad relay can cause the scooter to only start by using the kick starter.
8. There is no spark to the spark plug. The coil is bad and needs to be replaced.
9. Turn the key to the "on" position.

You need to check for a spark. There are a few ways to do this. The easiest way is to remove the spark plug and put it back in the spark plug cap. Then ground it to the engine - you should be able to lay it against a non-painted portion of the engine. Make sure there is good metal-to-metal contact. In a semi darkened area, attempt to start the scooter. You should see a definite spark at the tip of the spark plug. It's hard to see in direct light. If the color of the spark is blue, that means it's a strong spark. A white color is less strong, and a yellow color is weak. Most scooter starting systems are a bit weak (compared to cars). Even a yellow spark should start your scooter just fine.
The spark must occur at the right time. Just about all scooters made since around 1980 have an electronic ignition. These systems can rarely be set. In general, the spark occurs just before the piston reaches the top of it's stroke. There is a slight delay between the spark plug fire and the fuel-air mixture ignition. That's why the spark occurs a little early. Most ignition systems have an advance unit build in. As the engine speeds up, the time of the spark retards a little bit. This helps the engine fire the mixture at the proper time

There are a lot of tiny fuel and air passageways in the carburetor that must be kept clean it order for your scooter to run right. Carefully, take the carburetor apart. This can be relative easy (on a 50cc scooter). The carb has tiny passages that can get gummed up. Your scooter will not run correctly if the carburetor isn't completely clean, so take your time. I use a gallon container of carb dip (you can get a gallon at your local auto supply store).
First, remove all of the rubber and gaskets or they will get damaged. After a 20 minute soaking in carb dip, I blow out the carb with compressed air. You have to get all the jets and the passageways clean. Be sure the jets are clear, especially the starter jet. Sometimes carb cleaner won't clear out these tiny jets. Use a guitar or a piano string, a strand of copper electrical wire, or a tiny drill bit pin vise. Be sure not to increase the size of the hole in the starter jet or you'll change the tuning. Carefully reassemble everything, checking for cracks in the rubber carb boots and the gaskets. Replace them if they are old and cracked. Be sure and remove all rubber and gasket material first or they could get ruined. Spray carb cleaner also works if you're diligent.
If you have an electric choke, check it to make sure it works. Check the resistance between the wires - you should see around 10 ohms or less. Measure the length of the choke assembly. Remove the choke from the carb and plug the wires into a 12V source for 15 minutes. The choke body should be warm. Measure the length again - it should increase by around 1/8".
Next, consider whether your exhaust pipe is clogged. This is especially a problem with older two stroke scooters. The unburned fuel/oil mixture builds up in the exhaust pipe along with carbon over time. If the exhaust pipe is clogged, your scooter will run terribly or not at all. It can be difficult to tell if the exhaust pipe is clogged. The easiest way to tell is to remove it and try starting your scooter. It will be a bit loud - two strokes will sound like a chain saw. If it runs with the exhaust pipe off, you know that is the problem

hope this helps

John

There are a lot of tiny fuel and air passageways in the carburetor that must be kept clean it order for your scooter to run right. Carefully, take the carburetor apart. This can be relative easy (on a 50cc scooter). The carb has tiny passages that can get gummed up. Your scooter will not run correctly if the carburetor isn't completely clean, so take your time. I use a gallon container of carb dip (you can get a gallon at your local auto supply store).
First, remove all of the rubber and gaskets or they will get damaged. After a 20 minute soaking in carb dip, I blow out the carb with compressed air. You have to get all the jets and the passageways clean. Be sure the jets are clear, especially the starter jet. Sometimes carb cleaner won't clear out these tiny jets. Use a guitar or a piano string, a strand of copper electrical wire, or a tiny drill bit pin vise. Be sure not to increase the size of the hole in the starter jet or you'll change the tuning. Carefully reassemble everything, checking for cracks in the rubber carb boots and the gaskets. Replace them if they are old and cracked. Be sure and remove all rubber and gasket material first or they could get ruined. Spray carb cleaner also works if you're diligent.
If you have an electric choke, check it to make sure it works. Check the resistance between the wires - you should see around 10 ohms or less. Measure the length of the choke assembly. Remove the choke from the carb and plug the wires into a 12V source for 15 minutes. The choke body should be warm. Measure the length again - it should increase by around 1/8".
Next, consider whether your exhaust pipe is clogged. This is especially a problem with older two stroke scooters. The unburned fuel/oil mixture builds up in the exhaust pipe along with carbon over time. If the exhaust pipe is clogged, your scooter will run terribly or not at all. It can be difficult to tell if the exhaust pipe is clogged. The easiest way to tell is to remove it and try starting your scooter. It will be a bit loud - two strokes will sound like a chain saw. If it runs with the exhaust pipe off, you know that is the problem

hope this helps

John

Hi,,realy does sound like your fuel pump has had it,,did you have an inline filter,from the pump to the carb? anyway you could discard the pump and stick with good old gravity?

could be carbon deposit on the spark plug '' '' a bad coil or cdi unit '' '' clogged fuel pipe '' '' clogged jets in the carb '' '' clogged exhaust pipe

is choke working sounds like fuel problen

ebikes in bristol should help