I doubt the carb has a diaphram, as they are found mostly on 2 stroke engines. I think the carb has some obstructed passages or jets and these can be addressed without a rebuild kit. As to the ethanol in fuel, it's been in fuel 'round here for years and the only consequence I have found in any of my powered -2&4 stroke- equipment is the clear vinyl fuel lines get hard and either crack or come loose on their fittings.