I just bought this 1998 Polaris sportsman 335 I test drove it before I bought it. It ran great besides the battery being dead and having to use the pull cord. I got it home road around that day and the next. Then the next day I washed it with the pressure washer to get all the mud off from the previous owner. That night some friends took turns riding it up the road and back 2x people at a time. The last two to ride it were slightly heavier than the rest of us. (Not to be rude) the next morning when I went to ride it, it runs after the first or second pull but it’s sputtering and trying to die if I press the throttle then it will go if not it dies. It hardly goes in reverse no matter how hard I pressed the throttle. Also my headlights get dimmer when I accelerate until they are hardly any light. Any tips or suggestions on what it could be? All are appreciated.