The black rubber diaphragm in my Holley failed after two years of using California Gasoline. The green version is what you need. Just make sure you get the right size. There is also a smaller 30cc version. Very easy to fix. Simply remove the carburetor, turn it upside down, remove the four cap screws, remove the old one, insert the new one, put the cap on and reattach the carburetor. Fits perfectly. Do not work more than 30 minutes.