Her chee fun 50 scooter. when trying to accelerate the engine "dies". have had a new ecu and magneto fitted, carb stripped and cleaned, fuel tank drained and cleaned then filled with fresh fuel. when the air filter pipe to the carb is almost blocked( thumb over in-pipe) the engine will run ok. any suggestions would be great

Odds are that if it sat for a year with fuel in it, the carb may be gummed up. Opening the throttle will cause an immediate engine stop if it is not getting fuel.

I'd recommend a "clean out the carb" project, including using air to blow out allof the small orifices.

Hi Suzanne, a common fault with automatic scooters is the transmission or clutch. Your scooter has a centrifugal clutch which contains rollers, these rollers tend to wear flat over a period of time. You would need to remove the outer left side engine cover and the 'front' clutch to inspect the rollers. Unless you have an air ratchet gun to remove the crankshaft nut i would bring it to a dealer. Rollers are about 20 euros and the job shouldn't take more than a half hour, once they have your scoot on the ramp! Also check the condition of the air-box itself, make sure its not cracked/broken and connected properly to the carb, with an air filter fitted. Scooters make so little power that any change or variation in this area can seriously upset the fueling. Lastly check your spark plug and gap, must be clean and gap no bigger than 0.07-0.08mm. Best of luck..

A few things it could be, Dirt in the fuel line, or tank strainer is mostly clogged. Pinched fuel line. Plugged tank vent. Spark plug not gapped correctly, poor quality fuel, old fuel, 87 octane fuel that is more than a few weeks old.

It can also be a faulty magneto.

Replace the magneto that incorporates the sparkplug wire. The windings to the magneto are weak causing it to die out

what kind of bike is it?what style of carbs? if it has rubber diaphragms in the tops of the carbs, you might have a pinhole in one or more of them.

You have enough 2 stroke in the fuel? 50:1 ratio oil:fuel or more... it is a cheap engine needs extra lubrication..
-----
Is the spark plug clean? --- Is the HT lead connector to the sparkplug fine or has it come loose? --- Check the air filter - it could be wet or dirty or clogged - replace it if it has gotten wet or is dirty, on such a new bike it should look white as the driven snow... --- spray some carb cleaner down the intake while cranking the engine, and rev it up while spraying the cleaner in there, maybe you have some gunk in the carb messing up the jetting. --- Adjust the Idle screw to increase the idle (but not so high that the bike is tugging to ride off) --- Check through that lot and tell me how you get on.

check your takn and clean your fuel and air filter and check the fuel line from the tank to the carb and blow it out, 1 of these should help.

answered

If you did not completely disassemble the carb and remove all jets/emulsion tubes/needle valves then you did not clean the carb adequately. You could try adding either Seafoam, the Yamaha CARB-CL-EAN-ER, or Techron fuel system cleaner in an auxiliary gas tank and running the engine for a short while to ensure the mix gets into all the nooks and crannies. Let it sit for a couple hours to do the work, then drain out the float bowl, hook up the bike's gas tank and see what happens. Otherwise you need to remove, strip, clean, reassemble, and reinstall the carb.