Running problems

[handyrifle]

Its been sitting for a year and a half hasnt been started drained all old fuel out. When I start it it will die, but if I turn ingition on 3 or 4 times it will start and when it runs out of fuel it dies. If I keep my thumb on the throttle it will stay running when I let off of it it dies. When I start it I hold the starter button in and after it starts and still holding the starter button on stays running. As long as I keep high rpms it runs fine when I let off the throttle it dies. Need ideas and need help gotta race tomorrow.....Thank You handyrifle