Modern Vespa

I'm trying to figure out an issue with a friend's PX150. It will run for 30 minutes or so with no issue. Then dies. Doesn't want to restart. After 10-15 minutes it will restart and run just fine. Gas flows well, no kinks in the gas line. Cap breather hole is functioning. New plug and new cdi. I think it might be the LT coil. When it's cold the coil reads pretty close to spec - 525 ohms (white and green wires). When it's been run for a while, it's way out of spec - 689 ohms. Is this normal for the ohm value to change after running? Or is this possibly the issue? Or other things to check?

You should also measure the pickup (red to white). From what you describe points to the stator. Do you have spark when you can't start it??

The red and white measures 110 ohms, hot and cold.

Good suggestion, I'll run it until it dies and check for spark.

Mine did the same. Bad ground. In my case, it was the bit of shit metal that served as the mounting bracket for the coil. Once it finally broke and I created a new one, the problem went away.

edit: I replaced the coil as well... it could have been that, but the mount was garbage.