Sounds like a fuel problem, perhaps the fuel pump, or perhaps a leak in the fuel line (leaking air in, not necessarily leaking fuel out). When this happens no fuel will get to the carburetor so as you drive the carburetor will empty until the engine dies
What i would do next is
* Carefully inspect all the rubber fuel lines to ensure they are not cracked anywhere (it is most common to crack near the ends). Replace any damaged lines
* Inspect the fuel tank cap. If it is plugged it will cause engine to slowly run out of fuel
* Perform a
Fuel pump pressure test (both tests)
Fuel Cap Test for all B210 Japan-market models:
* You should not be able to blow air out through the cap
* You should be able to suck air in through the nubbin
1. Wipe valve housing clean and place it in your mouth.
2. Inhale air. A slight resistance indicates that the valve is in good mechanical condition. Note that, by further inhaling air, the resistance should disappear as the valve clicks.
3. If valve is clogged, or if no resistance is felt, replace cap as an assembled unit.