+1 on Jackscycles and Stu.
Std jetting recommendation from GGUSA is:
2004-05 TXT280-300 PRO WITH PHBL26 (26mm) SEA LEVEL TO 3,000 FEET
MAIN: 118 (115 OK, NOTHING SMALLER!)
PILOT: 36 (38 OK)
NEEDLE: D36 (3rd, or 2nd CLIP POSITION DOWN FROM TOP)
FUEL SCREW: 3.5 TURNS OUT
FLOAT HEIGHT: ARMS IN LEVEL PLANE WITH FLOAT BOWL BASE (PARALLEL)
My recommendation for optimal trials use is: (I live in Mass)
Needle: D36 - clip - 2nd from top
Fuel screw - should be around 3 turns out - but needs to be set with lean bog technique.
IMO - the PHBL likes a rich pilot for the most power off the bottom. If you want a smoother delivery off the bottom with less power then go leaner.
If you do any sustained road work or ride real fast trails - stay with the richer main and needle setting.above.