Hey - here´s a simple, obvious idea but it took me weeks to figure out back in the 70´s... Have you cleaned the baffle tube out recently? Two-cycle engines are very sensitive to back pressure. Use an impact driver to undo the screw retaining the baffles, right at the end of the exhaust. Then pull out the baffles (twist and pull) and remove any glass fiber wadding at the end and discard it, then burn off the \