Or the balance between carb's could be way off IF it has fuel and correct ign timing. This winter i did some work on a Tiger 6 with a X Flow, initially i just needed to make a new remote gearlever, the guy swore it drove up the trailer but in the end i replaced all 4 mishab, there where no end washers and nuts on the Webers i changed the dizzy as the gear was badly worn, replaced the Lumenition trigger wheel as i could rotate it more than 5 degrees !! the central carbon in the dizzy had no spring action anymore and i changed the clutch as i couldn't engage gear because a few fingers on the pressure plate where off on top of that the diff sounded like a bag of nails, turns out someone changed the ratio without proper adjustment