Recently purchased a 1979 GS 850 in original condition. I had previously owned one for 17 years until hit by a car. Really liked the bike and always wanted to get another one. Problem I am having with current bike is it leaks gas out of the overflow tube when parked. The fuel petcock does not have an off position to make matters worse. I was told by a local shop that if you disconnect supply tube from petcock and gas runs out, then petcock is at fault. Is the bigger or smaller of the tubes? Also dirt can be flushed out of the carbs if you loosen the screw and drain the gas out of the bowl. Let me know your experiences with this and if anybody knows of an aftermarket petcock with an off position.