cujet,
You are correct with your annalist on how the engine will react when placed under a fast load ie: motor starting. Then you are also correct about manually throttling the engine to full load would not enough. There is one thing you missed and it is the most important. The stored kinetic energy "within" the flywheel on the generator "exceeds the stored kinetic energy on the heavy flywheels on the 14/1. This is my pulley from Mike on coppermine:
SuperMax Flywheel/Double PulleyThe pulley shown weighs around 120 lbs and is built with three pieces, making it a modular construction so that custom pulley diameters can be easily upgraded or changed. The flywheel section weighs 70 lbs and is 13" diameter and 2" thick. These pulleys use a standard SK taper bushing. This one is for 600 and 850 rpm, 7 7/8" and 11 3/16" diameter pulleys
To see what is happening in slow motion. A large motor is started, this places 3 to 5 times the running wattage momentary load on the generator head for 2 -3 seconds. The generator head is oversized for two reasons. First, it provide plenty of head room for high surges and it has a much heavier rotor than a smaller generator head, also the bearings are much larger than if I used a properly matched head. This extra strong shaft and bearings allow me to place a flywheel/pulley system weighing over 120 lbs. without over working the bearings and reducing bearing life.
Now if I used a properly sized head 7.5 kw, the rotor ( I haven't weighed them but its close) would be about 60 lbs. The rotor on the 20 kw would be 120 lbs. approx. I have 120 lbs in a small diameter (rotor) spinning 30 times a second and a 120 lbs flywheel/pulley in a 10.5+ inch average mass diameter spinning at 30 times a second. This is just in the generator head alone, the produced surge has to overcome and slow down this stored potential before it even starts to place a load on the belt then to the engine. Then the engines flywheels stored potential assist the generator head stored potential. As far as slowing the engine down, since the surge has to slow down both flywheels, the slow down would be much slower than if the load was suddenly placed on just the engines flywheels, therefore the engines governor can more accurately follow the power requirement needed, without the stored potential in the generator head the engines governor and engine could not meet the demand nearly as well.
This is no fix all to replace an electronic governor with a properly sized generator head, what I'm trying to archive is having a somewhat tighter frequency regulation when multiple motors are engaging at once ie: refrigerator, freezer, well and not have to worry about unacceptable frequency drop without any electronic controls. You are also correct with the poor sine wave under lighter loads. Everything is a give and take in this world and this is the way I do it and as you and Doug point out very accurately it has it drawbacks as well as it's strong points.
Thanks for your input
Diesel Guy