I've got a 70's H35 that runs and idles good. Just tuned up and rebuilt carb. The problem is that when not running, gas will run out of the back of the carb. The cheap fix has been a gas shutoff valve at the tank. My guess is something not seated correctly and allowing gas to push by in the carb. Any thoughts on this? Also, I'm not really using this engine and may try to sell. What would be a fair asking price? Other than the carb issue it's in good condition, compression, new points condenser, plug, carb gasket kit, replaced gov shaft and linkages. Thanks.