Have a Icebear Fuerza 125cc.. 297 miles. Bought brand new. Been running great until a few days ago I noticed a gas leak in fuel sending unit. Fixed that but in 4th (4 speed) it jerks as accelerating, and I mean hard. Doesn't want to go but it will and it's rough. Changed oil at 225miles. Cleaned carb after all this, chain lube and spark plug. Still doing it. Played with the choke at different openings, no go.. now I have no clue.. thoughts????