Some possibilities:
- Air getting into the fuel line. (Try borrowing a friends' hose. Check for pinholes, loose clamps / gaskets, etc. in all suction lines.)
- Weak fuel pump. (If aggressive primer-bulb action keeps it running when it starts to miss, the fuel pump is a prime suspect.)
- Ignition misfire. (CDI modules tend to fail as sudden-death, rather than as gradual / intermittent deterioration, but it's possible that something's misfiring when it gets hot. Check that the
plug wires are making good contact and aren't coming loose or deteriorating.)
- Crud in the carb. (They do like periodic
cleaning. Which reminds me, I should do mine this
winter...)