take the carbs apart sound like the needel and seat is stuck if it sat for 3 years you can almost bet on it. set it up per the spec in the book and dont forget to set the pop off press correct very important if you want it to run right. and to prim it off spray some carb spray in the air intake but be carefull that ski mixes the oil in the carbs. so no fuel no oil then all that work rebuilding would be for nothing