Serious Fault. Cut out on motorway. Help troubleshooting?

[amorti]

Also worth replacing the fuel vacuum hose. When it gets hot it can collapse in on itself restricting or cutting off fuel flow. Fairly common issue on nc30's. It's the hose that attaches to the small spigot on the fuel tap, and runs to the r/h rear cylinder under the carbs.

Rick Oliver sells some thicker walled tubing that won't do this.

Yeh that. I would use silicon tubing to replace any wron vacuum tubing. Also check the tank vent.

If it does it again, open the tank slowly and listen for air rushing in, if yes you have a blocked vent.