Is something seriously wrong??

[Brizz125]

I have owned the xmotos 250cc for 2.5-3mths now and it has run perfectly until last weekend.
Under load and at high revs it seems to retard or starve for fuel. It coughs and splutters and just doesn't wanna run.
We have tried replacing the spark plug, the cdi unit, was thinking it could be the coil gone or the lead.
Does anyone have any ideas as to what it could be?
Any help is urgently needed.

 

[Sidney]

Was it low on fuel??

 

[Brizz125]

umh no...
Tank is full..
Have even flushed tank completely and replaced with new fuel, as we thought it could be stale fuel..

 

[Custom]

could be fuel starvation. give it a $2 tune. start and warm the bike, remove the air cleaner, then rev it as high as your comfitable then slap your hand over the carb at the same time pulling full throttle. just a quick slap and let the bike clear the fuel while holding full throttle. do this a couple of times then try riding it. ive had to do this with my bike a few times and done it alot with the many cars ive had over the years

 

[blackdog]

If it has a fuel filter, try running it without the filter. My Lifan 140 had a similar problem. Took me hours to find out what was wrong. Replaced the CNC filter with $5 see through one, bike runs perfectly now. Just a thought.