Check for bubbles in the fuel line between the needle and carb, that is the standard problem, plenty of posts on here about it. If you are getting them, it will be leaning out the engine, potentially causing preignition.

I do not have any such problem running mine on an APC 15x7. To cure the bubble problem I cut the needle valve assembly of the back plate and attached it to the firewall.

Also your idea of using a check valve is not a good one without a regulator to control fuel flow. As you run the engine, preasure will change in the tank, causing changes to the amount of fuel being forced into the carb, it will get richer over time. If you then lean it out, it will be too rich when the preasure drops. You need a regulator such as the Cline or Iron Bay.