As we know mower engines need a certain amount of rotatable mass to stop the motor kicking back on start up and low rpm .
The alloy cone clutch with the light alloy flywheel doesn't seem like it would be enough to overcome the kick back problem.to me unless the alloy cone clutch is a lot heavier than it looks ( eg has a metal weight cast inside it)
I've never owned or worked on a Scott Bonnar reel mower so I can only comment on what I see from the images but I don't think the alloy cone clutch has a heavy weight cast inside.
Mower manufacturers don't always use a cast iron flywheel to increase the rotatable mass when using a light rotatable mass on the pto side of the crank (eg alloy cone clutch / alloy pulley ,light bar blade with light boss)
I quickly had a look at 3 Flywheels 2 Wipac and 1 Phelon ,I have limited knowledge on Scott Bonnar reel mowers but have seen a few removed Kirby motors ,I saw Scott Bonnar motors using Phelon Flywheels but have no idea what type of cone clutch was originally attached to these motors .
Looking at the 3 flywheels I have ,the light Phelon flywheel weighs 620 grams ,the light Wipac is 650 grams and the heavy Wipac is 1,360 grams ,so I would think the light alloy cone clutch would use a heavier Wipac or heavier Phelon flywheel compared to the Kirby motor with the heavy cast iron cone clutch.
The heavier alloy flywheel weighs more than 1 litre of water and a little more than double the weight of the light alloy flywheel.
That's what I was thinking looking at the parts but can't confirm without more info or having the two different Scott Bonnar cone clutch mowers in front of me.
