Modern Vespa

I have an LX50 and i've had problems with my bike for the past couple of weeks now while trying to fix it.

The problem is when I go full throttle the power cuts out fully with random stints of giving it power. This means when I have to go up onto hills my bike is only going around 6mph which is very dangerous for other road users and also me.

I've cleaned the carb but it seems to have no difference, I am going to check the air filter and also fill it up with redex and see how that goes?

If anyone has any idea please reply, thank you

Could you be more specific? Does it cut out after getting up to full speed/rpm, or does it cut out with the throttle open BEFORE getting up to full speed? Can you get up to high RPM by blipping the throttle with the scooter on the center stand?

Periodic problems are generally not caused by the frequent carb issue of gunk clogging the jets.

Lots of other things to think about:
- the rubber diaphragm on the back of the carb could be creased, creating an air leak at high throttle (note, I am not positive the 50's carb has this diaphragm)
- other air supply problems - cracks in pipe leading from filter to carb intake, dirty/disintegrated air filter, bad seal around filter cover
- cracked vacuum hoses from the carb could be preventing the fuel petcock from opening properly, or the petcock valve could be sticking closed from age, so the engine is sputtering from lack of fuel
- the float valve inside the carb is set too low, so fuel isn't coming into the carb fast enough at high speed
- the plug is fouled or the wires to it are loose along their path between the plug and the CDI
- due to old rollers, schmutz or oxidation on the variator bushing, or gunk on the clutch pulley mechanism, the transmission is sticking in high gear, so when you accelerate from low to high speed the engine is lugging

Yes it cuts out before getting to full throttle.

I've edited the title of your post to something less alarming.