I read on a post the other day about a spray that could be used on some engines. I found a value on the engine that looks like an air value stem but the value has a crack running down its length. I am not sure if that could be part of the problem also. I am hoping that the value and or the spray will help. I am having a problem were the engine will not run over 1300 rpms and after looking at the engine I am not sure I should try to work on the carbs my self.