Sym megalo 125cc cuts out all the time

SOURCE: 125cc yz motor flooded and wont start.

Start with a new stock NGK spark plug. Check for spark. If spark then do the following > >
Remove the water trap bowl at the bottom of the petcock, (gas valve). Any water or trash in the bowl? Drain a cup of gas from the tank. Any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the two screws on the outside throat of the carb and spray into the screw holes as well.
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Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine. Set the idle speed with the idle screw. This process should get you back on the road.

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SOURCE: backfiring atomik 125cc running rough.

What octane gas are you using? If octane is to high even with mixed fuel it will cause valves to burn out run to rich....try using lower octane gas, if not you need to adjust fuel mixure...only ned a small screwdriver for this....but try the fuel first...

SOURCE: 2002 gsxr 600 cuts out full throttle

if this bike is carbureted i would say your main jets are plugged.

SOURCE: i have sym jet 50 99 reg it just cut wont start

Is there a spark at the plug? if so its likely to be fuel related... is the plug getting wet? if so its likely to be air (or spark) related
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SOURCE: Engine cutting out when open throttle. YAMAHA NEOS 50cc MOPED

i had a simuler problem with my honda cr 250 moto-x bike it would start fine and you could keep it ticking over with the throttle(i have deliberatly unscrewed the tickover in case i come off,it will cut out) when i got on it,it would go for about 400-500 metres then splutter and die and not start again for around 5 mins. i immediatly knew it was a fueling problem. so after stripping the carb and giving it a good clean out i was baffled when i got back on and it still done the same. i then dismantled the fuel tap cleaned it all out and put it back together and tested it,it was very very slow so i unsrewed my fuel cap a little and was greated with the familur gush it should deliver. problem solved! the vent in my fuel cap had crystalised up,so the fuel was coming out but the air was not getting in,causing a vacuum and slowing down the flow and basically emptying the carb quicker than it can fill back up!!! clean your carb,fuel tap and any vents in your cap or tank. if this does not work then your bike must be over fueling or low on compression.