I HAD THE SAME PROBLEM WITH MINE WHEN I PUT THE 70CC KIT ON AND I FOUND OUT IT WAS THE FUEL PIPEING THE ROUNG WAY ROUND MAKE SURE U HAVE THE BOTTOM PIPE WOT COME'S FROM THE FUAL TANK GOES ON THE CARB AND THE TOP ONE GOES ON THE INLET FROM THE CARB TO THE ENGINE BECAUSE IT CREATES A VACUOM MAKE SURE U HAVE CLEANED YOUR JETS IN THE CARB BEFORE PUTTING THE CARB BAK ON IT WORKED FOR MY SPEED FIGHTER 2
AARON PHILLIPS, February 2008