Topic: Honda CB 500 Fuel Issue

[shira]

Hello,

We have a 1973 Honda CB 500. Since we've gotten the bike we have only been able to ride it 50 miles before fueling it up, even after switching to the reserve tank. When we look inside the tank, there is about a 1/3 a tank of gas, but unless we fill it up, it won't start or run. I'm wondering if anyone else has run into this and what to do. We've taken it to two mechanics and spent a lot of money already on it, and would love to hear your thoughts. Neither of us are very mechanical but at this point, we don't just want to keep throwing money at the problem. We've had the carbs cleaned, new jet kit, replaced seals, replaced points plate and had everything adjusted, calibrated and all that.

[brooze72]

Welcome aboard!  Sure sounds like a fuel issue.  Check your petcock filter and the vent in the tank cap.  Do you have external inline filters?  If so, check fuel line routing, it must be a continuous & gradual descent to the carbs with no loops upwards.

[Frostyboy]

+1 to what Brooze said. Your petcock is different to mine, looking at a pic of the K2 petcock there isn't a filter in the tank itself like mine. Maybe take the petcock off the tank & check to see if the reserve port is blocked?
If the filter screen in the petcock bowl is blocked, it may be relying on the weight of fuel above it to pass through a partially blocked screen.
Also check that the overflow/vent tubes to the carbs aren't blocked up. They're the ones that come off the bottom of the carb bowls & run over the back towards the centre stand.

[shira]

Thank you!!! I will try these things.

[78 k550]

Welcome,

Paul

[Rgconner]

When I was suffering from a similar issue there was a bit of steel wool left over from the Painter in the tank.

It rusts, then clogs up the filter something horrible.

[Scott S]

 That petcock should be rebuildable, too. Take it apart and make sure the passages for reserve are open. New rubber gasket and o ring.

 However, only 50 miles? Sounds like it's running awful rich or dumping fuel out of the carb overflows. You should get at LEAST 100 miles before reserve, if not 120 plus.