Which thread fuel tap does the Honda CX500, GL500, CX650 or GL650 require?
Keep in mind that the outlet on the fuel tank dictates which size petcock you need; we have had bikes in the past which have had their fuel tanks replaced with one of a different year which means that the anticipated petcock size doesn’t match. If in doubt, measure the outlet size.
The vacuum petcocks are not provided by Honda any longer, though there are aftermarket options on eBay for the GL650 which presumably work for the other models with the same thread size on the tank. They’re linked to below.
| Country | Year | Model | Petcock Thread | Part No. | Genuine or Vacuum Replacement | Aftermarket Replacement | Notes |
|---|---|---|---|---|---|---|---|
| USA AU? | 1978 1979 1980 | CX500 | 14mm | 16950‑385‑701 16950‑385‑702 16950‑385‑703  | eBay US | eBay AU | |
| USA | 1981 1982 | CX500 | 18mm | 16950‑449‑841 | eBay US | Vacuum petcock from factory | |
| AU | 1981? | CX500 Shadow | 16mm | ? | Non-vacuum petcock from factory | ||
| USA | 1981 1982 | GL500 GL500I | 18mm | 16950‑MA1‑731 16950‑MA1‑732 16950‑MC9‑830 | eBay US | eBay US | Vacuum petcock from factory |
| USA | 1983 | CX650C | 18mm | 16950‑ME8‑005 16950‑ME8‑015 | eBay US | eBay US | Vacuum petcock from factory |
| U SA | 1983 | GL650 GL650I | 18mm | 16950‑ME2‑000 16950‑ME2‑010 | eBay US | eBay US | Vacuum petcock from factory |
| Worldwide | 1983 | CX650E | 18mm | 16950‑ME2‑000 | eBay US | eBay US | Vacuum petcock from factory |