Run one hose from each petcock spigot to one carb inlet. Do not add a hose between the bowls. On this 1976 CB500T the carbs went back on with the lines off, and the first diagram that got offered had a crossover those carbs do not have. Looking at the nipples settled it.
Each carb has two barbs. The inlet is the one the petcock feeds. The other is the overflow. It hangs down and ends under the seat. A stuck float then spills where you can see it, instead of filling a cylinder.
Which hose is which
| Hose | From | To | Shop |
|---|---|---|---|
| Left inlet | One petcock spigot | Left carb inlet | View Left inlet (affiliate) |
| Right inlet | The other petcock spigot | Right carb inlet | View Right inlet (affiliate) |
| Overflow, each carb | The second nipple | Open end under the seat | View Overflow, each carb (affiliate) |
Affiliate Link • Earns Commission
The hose
Old vinyl cracks and swells on ethanol fuel, then a crack becomes the lean condition that shows up as a dead idle once the enrichener is off. Replace cracked line. Measure the nipple with a caliper or by test-fitting a scrap before you commit to a diameter. On these twins the inlet is commonly 1/4 inch. Confirm it on this bike.
Gates 27027 is 1/4 inch inside, 2 feet long, SAE J30R7, rated for gasoline and ethanol blends up to the legal limit. Gates rates it for low-pressure fuel and PCV duty, not for a fuel-injection rail. A carbureted CB500T is the low-pressure case. Two feet is one path. Both inlets plus two overflows need more than one pack.
Clamp the inlet hoses. The overflows on this bike had none, and an overflow can live that way because it is not under fuel pressure from the tank. An inlet without a clamp walks off the barb the first time the tank is full. Keep the new line off the exhaust and off the throttle cables. A hose that props a cable is how the slides stay open.