Long story short. Have a 79 Kaw 650 SR. Sat for 20 years. Carbs were shot. Had someone get it running. Think they put some 80' carbs on it. The bike ran but backfires when backing off the throttle. After last ride smelled gas. Gas leaking from overflow. Wouldn' stop so I took off the gas tank. When I took off the tank gas, dripped from fuel tap. This is one of those taps that shut off when bike is turned off (vacumn). Would it cause the carbs to fill and overflow, or do I have carb problems?