SunL go kart with 250cc GY6 engine

[jstwondering]

I have a Sunl go kart with a 250cc GY6 engine. There is a vacuum operated fuel valve in the bottom of the fuel tank. I am not getting enough vacuum to operate this valve reliably. My vacuum gauge indicates around 7mm at idle and goes to 0 when I rev the engine. I tried adjusting the valves and see no change. New carburetor, new carburetor manifold, new vacuum tubing. Waiting on a spark plug adapter so I can check compression. Does anyone know if this engine has a compression release that may be stuck and causing something like this. Any other ideas?

 

[Twinky]

Chatgpt answered like this on your question :

It's possible that a compression release could be causing low vacuum, but it's not very common. Other potential causes could include a worn or damaged valve, piston rings, or cylinder wall, as well as an air leak in the intake manifold or carburetor gasket. It's also possible that the fuel valve itself is faulty or clogged.

Checking the compression is a good next step to rule out any internal engine issues. If the compression is low, it could indicate worn piston rings or a damaged cylinder wall. If the compression is good, you may need to further investigate for air leaks or other issues in the vacuum system.

 

[jstwondering]

Chatgpt answered like this on your question :

It's possible that a compression release could be causing low vacuum, but it's not very common. Other potential causes could include a worn or damaged valve, piston rings, or cylinder wall, as well as an air leak in the intake manifold or carburetor gasket. It's also possible that the fuel valve itself is faulty or clogged.

Checking the compression is a good next step to rule out any internal engine issues. If the compression is low, it could indicate worn piston rings or a damaged cylinder wall. If the compression is good, you may need to further investigate for air leaks or other issues in the vacuum system.

Does this engine have a compression release. I've been told it does not. What vacuum reading should I get at the 5mm outlet from the carburetor manifold? I will check compression today. I am running it with a gravity fed fuel system now. I replaced the vacuum operated valve with a manual petcock. Once I get fuel to the carburetor it runs great.

 

[jstwondering]

Does this engine have a compression release. I've been told it does not. What vacuum reading should I get at the 5mm outlet from the carburetor manifold? I will check compression today. I am running it with a gravity fed fuel system now. I replaced the vacuum operated valve with a manual petcock. Once I get fuel to the carburetor it runs great.

Found my vacuum leak by using starting fluid. Spray the area of possible leaks and see if the engine reacts. Works great. Turns out I have a carburetor with a 30mm diameter going into a manifold with a 33mm diameter. The clamp is not able to make an air tight connection with this mismatch. I am getting some compatible parts to solve my problem.