To find an air leak in the fuel system of a Massey Ferguson HD2650, the following steps should be taken:
1. Visually inspect all fuel hoses, clamps, and connections for splits or cracks. Replace any damaged parts.
2. Check the fuel tank for signs of venting. Install a new fuel tank vent if one is missing or if it appears to be clogged.
3. Extend the fuel line as much as possible to ensure that it is free from air pockets. Use a funnel to pour clean fuel into the fuel tank while it is still cold.
4. Clean the inside of the fuel filter and housing with a clean cloth and inspect for any leaks or blockages.
5. Install a new fuel filter if it appears to be clogged or damaged. Make sure the fuel strainer and clamps are tight and in good condition.
6. Connect the fuel line and start the engine. Inspect for leaks at the fuel line. If a fuel leak is observed, adjust the fuel line to make a tighter seal.
7. Replace the fuel line or fuel filter if necessary.
8. Inspect the carburetor for leaks and clean or replace it if necessary.
9. Check all of the air intake gaskets and seals to ensure they are secure and free from leaks.
10. Finally, if the engine still seems to be running rough or is leaking fuel, it may be necessary to have it professionally serviced.