Bike cutting out at Full Throttle (50cc Scooter)

[JamesNRG]

Piaggio NRG Extreme AC 2003;


Hi,

Recently, my bike has been cutting out or bogging down at full throttle, Anything below half throttle is fine, but this is strange as it was fine a few days ago, was happy at fully throttle, but now when i open it up from a slow speed, the rev's will die out and stall, if i do it at high speed, it sounds like im chopping on and off the throttle then it will bog down.

Any ideas what it could be?


EDIT: I also have stiffer Clutch Springs to aid my pullaway, to allow it to rev higher before the clutch engages, it was fine until i came off, now its pulling away in the dead zone bogging, and if i stop on a hill, it will not move, at all...

The Bike has a Doppler S3R (Performance Exhaust) if that helps and has had the Main Jet upjetted from a 56 to a 60.
Thanks.
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600bhp 50cc power!

[senso]

Have you already swapped the spark-plug and cleaning the air-filter.

[SpannerMonkey]

https://www.petrolmag.net/view/articles/how-to/carb-guide/
That should help

[JamesNRG]

[Glenben92]

I'd say put the original jet back in seems the reasonable option. fuel flow is controlled in 3 different stages

1- idle screw
2- needle position
3- jet size

it moves through the three as the throttle position increases. so at full throttle, jet size is determining the amount of fuel getting into the cylinder. and your symptoms sound like it's overfuelling, so try the old jet
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57 Huoniao HN125-8 - , 97 Kawasaki GPZ500S -
99 Yamaha FZS 600 -
Mod 2 Passed - 01/10/2010

[JamesNRG]

[senso]

What is the sparkplug tip color?

[JamesNRG]

The tip is like colour of a cuppa tea, but the thread is all black and wet.
____________________
600bhp 50cc power!

[senso]

When the carburettor is tuned properly the spark-plug tip will have a light brown(ish) colour, the threads is typical that they become dirty and even wet with some kind of oil residues, that looks like a dirty air filter, the carburettor doesn't detune by itself, or it should do it, as the tuning screw as a spring to prevent that.

[JamesNRG]

When i come home from work i'll get aphoto of it, so you can tell me if the colour is correct or not Ill also clean my air filter and check my rollers.
____________________
600bhp 50cc power!

[SpannerMonkey]

[JamesNRG]

[senso]

So your problem is a simple tuning issue.

[JamesNRG]

[SpannerMonkey]

Rollers wouldnt cause engine to misfire and/or die =/

[senso]

The thread becomes sticky and greasy because the seal between the thread and the cylinder isn't perfect and the oil that is mixed with the gasoline isn't totally combusted during the combustion and expansion cycle of the engine, so some part of the oil lubricates the crankshaft, crank bearings, con-rod and is bearings, and the cylinder liner and the piston, and the seals of the piston, and there is yet enough oil to produce the smoke and to make those sticky residues.
All this being said, what brand of oil do you use?
And what is your carburettor?
Did you changed the needle position the last time that you have been playing with the carburettor?
A good starting point to tune the carburettor, is to screw the tuning screw, I don't know how it is called in English, but your carburettor as one idle screw almost in the middle of the carburettor body and other screw near the air filter, usually in the same side of the idle screw but is smaller, if you screw that screw all in(be gentle as the carburettor body is soft and the screw is made of soft brass), and the unscrewing 2 turns it should become better than its now, and then try screwing or unscrewing a quarter of a turn no one side, if it gets worse move it to the opposite direction.

[JamesNRG]

I use Castrol TTS (2 Stroke, Fully Synthetic) Oil, the Carb is a Dell'Orto 17.5mm, haven't touched the Needle, just the Idle Speed and the Pilot Screw. I'll try what you said tomorrow, and see if there is anyluck, as when i go full throttle, the engine tone deepens and just bogs out, or goes powerless.
____________________
600bhp 50cc power!

[Glenben92]

exhaust wouldn't make it run lean with stock jet :S air filter would. if the air filter hasn't been changed at all then the newer jet will be richening you too much. and you could try giving the carb a good THOROUGH clean? bad luck about some idiot cross threading it, never understood how people are stupid enough to do that. really gets to me! good luck mate
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57 Huoniao HN125-8 - , 97 Kawasaki GPZ500S -
99 Yamaha FZS 600 -
Mod 2 Passed - 01/10/2010

[Jorge]

I can gaurentee you have water in you carbourator give it a clean or drain it. i had this tediouse problem with my 50cc scooter.
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HONDA NS125R-K

[JamesNRG]

How would i get about cleaning/draining my carb? I'm guessing it has to be off the bike and the bike outta use for a day or so?
____________________
600bhp 50cc power!

[Jorge]