Motorcycle Repair: 1983 yamaha 750, fuel hoses, tank interior

Question
i have a 1983 yamaha 750 it has sat for about two years and the carbs were rused inside but cleaned up good now the gas and oil is pumping into the breather what is wrong but the moter started and sound great i did not let it run but only about a min. thats when i notice the gas and oil going in to the breather help please  

Answer
Hi Jaws,

Gas in the airbox is caused by needle vlaves (float valves) not sealing. Causes are varnished pin springs in needle valves, rust particals or other debris caught between needle valves and needle valve seats, worn needle valves and seats.

Fuel may have flowed the other direction and entered into the oil as well.

Requires checking and possibly replacing needle valves and seats. Consider sealing/lining the fuel tank interior with a product such as Kreem. This will help keep rust from entering the carbs and preserve the tank.

Install a fuel filter or change the existing fuel filter.

Clean and/or replace the petcock.

Check all fuel hoses for evidence of varnishing or other contamination built up on the interior walls. Replace hoses as necessary.

Respectfully,
Mark Shively