Honda, like many other manufacturers, recognizes the prevalence of ethanol in modern gasoline blends and designs their components to withstand its effects.
To ensure accurate and up-to-date information regarding the materials used in your CT70's carburetor components, I recommend consulting the official Honda documentation, such as the service manual or contacting a Honda dealership or authorized parts supplier. They can provide you with the most accurate information based on the specific model and year of your CT70.