My cousin has a 01 blaster that will run and gets a weak spark. Then it just dies, its not the idle and seems like na electrical problem. Any ideas? He tested the cord the spark plug attches to and its not that or the part that attaches to that cord (sorry im not sure on the names of the parts)

 

my first guess would be the ignition coil. They sometimes act up after the machine runs for a bit, something inside gets hot and it expands and the ciruitry opens up. It also could be the CDI box, the part that runs the coil, or the flywheel and stator, which signals the CDI of crankshaft position. Consult a manual, will give you step by step instructions how to check things