Yamaha Jog RR throttle problem

Been riding a Peugeot Trekker (2000) for 2 years and just changed to a
newer (2004) Yamaha Jog RR for something a little more light and
sporty.

It runs and the acceleration is good however everytime I open the
throttle above 50%-60% it seems to just lose power and if left with
open throttle it coasts to a stop with the engine cut out.

I assume there is some kind of fuel starvation
Whats the most likely cause, blocked fuel line or carb needle, lean
fuel mix?

Also whats the best way to clean a scooter carb if I do take it out to
strip and clean?

It sounds like your main jet is plugged, Pull the carb and clean the jets,
Paul

mainjet's not plugged. If that was the case, it would start fine, idle
fine, but as soon as it reaches somewhere between 1/4 and 1/2 throttle in a
steady state (Opening at which the mainjet essentially takes over from the
pilot jet) it wouldnt run. If it was the pilot it wouldnt start. It is
definitely a starvation problem, the question is why. You havent said
whether this is a new unit or one purchased used. Speaking as a former
yamaha service tech, new or used can make a big difference to the pool of
possible diagnosis. If new, it could be something as simple as a misrouted
and kinked fuel line, but quite probably is grit in the fuel impeding proper
operation of the float needle. If it is a used bike...omigawd it could be
nearly anything. Did the previous owner reset the float height? (possibly
in an attempt to stop a chronic overflow condition from grit in the float
needle?). is the carb stock? Is there a fuel filter present? Is it partly
plugged?
You dont give a timeframe either. How quickly, under full throttle, does it
display this behavior? If quickly it's probably the float issue. If not
quickly perhaps a gas tank vent blockage. The tank vent blockage can be
easily tested. go out with the gas cap on loosely or not at all. Try and
re-create the conditions and see if the behavior persists.
I dont think its a choke issue. It will generally run with the choke on,
just won't idle when hot, makes a bit less power everywhere and it runs
rough but should start to clean out a little under sustained high rpm
operation.
Hope mr platypus doesnt object to my non-UK diction.
salut....John

Yamaha Jog RR throttle problem - Advice Please