Unless the truck is being fed fuel from an outside source (its own crankcase, for example), or unless there is a governor problem, it won't hurt itself going to full throttle in neutral.
Carbureted engines are "governed" by the amount of air fed to them - they then draw an appropriate amount of fuel - and thus can keep accelerating beyond their limits.
The Multifuel is oopposite, it's RPMs are controlled by the fuel being fed to it. and it injests the appropriate amount of air. Shutting down without the cutoff cable is just an annoyance, not a hazard. In a parade, push it in neutral.
Trucks that have been sitting may have issues with the shut off in the IP sticking. And "new purchases" have unknown factors (condition of governor, etc.) making it wise to be prepared to suffocate the engine.
The real concern would be "extra" fuel being fed the engine via flame heater, crank case oil, flammable gases in the atmosphere (ether, propane, etc.).
Lots of the ventilated crankcases seen on Multifuels are from running downhill - the truck can push the engine to RPMs beyond the governor setting - and beyond the engine's specifications.
Regards,
David
