I've had that issue many of times with these type carbs. I think it's the alc in the gasoline . Not too kind on the rubber diaphrams . Ethyl free gas should help them last longer .Turns out it was the metering diaphragm and replacing it solved my above mentioned problem. The check valve (high speed) is still broken which does food fuel out the 4th jet during priming. I don't mind it but it could be a problem in the future.