Problematic "check valve" (actually a main jet) diagnosed. Both the clogged jet orifice and the stuck rubber check valve diaphragm removed, disassembled and serviced. Replacement, not repair, is the accepted industry standard procedure. Very tiny, near microscopic work involved. For size reference, a 10mm socket shown in pic. The little brass check valve is pressed (rather than screwed) into the body. The tiny black circle is the diaphragm which is captured in the nozzle end of the valve, held by 4 tiny spring arms. 3 Fuel openings are visible. This'll be a runner tomorrow.