mileage drop

[android12]

I tend to see a significant mileage drop from about 44 to 32 every year or so, usually after sitting in the winter. Usually I put in a good dose of carb cleaner and it improves. Im sitting at 15k miles had valves adjusted and carbs synched at 6500. Plugs and air filter only 4k old. Anyone else see this? Anyone else need a carb synch or valve adjustment this soon?? Is the STP carb cleaner ok? Thanks in advance.

[PaulVS]

Most carb cleaners don't do squat for gummed carbs.

Get a can of Seafoam and run as a 50/50 mixture with gasoline.  It will run like hell while you're running the mixture, but it will clean up the carbs beautifully.

I've done over 50% STP carb cleaner in the past and it didn't work.