HELP i've got a yz 125 08 and after ridding when I pull up it cut's out , any ideas.

are you saying it won't idle ?

spot on , it just dies but kick's over first time afterwards.

turn up the idle . turn the idle knob or screw clockwise (I think) turns the idle up.
on some bikes the choke knob doubles as the idle adjustment .
do not mistake the air screw adjustment for the idle adjustment .
most 2stroke mx bikes are set up to not idle for lots of reasons.

idle time will inevitably lead to plug fouling though.