Flywheel mass (heavier)

[Rainmaker]

I noticed Lyndon P changed to a heavier flywheel for the Erzberg enduro. Has anyone done this?
What were your reasons?
Is this part available for sale or was it a special factory racing part?
Video (about 6:00 minutes in):

 

[rayivers]

I haven't done this to my MXR, but fwiw I've done the reverse to one of my ICE bikes. I replaced a 6.5 lb. external-rotor ignition with a 1.5 lb internal-rotor unit, then had the crank rebalanced (22 grams removed). It changed the throttle response from somewhat sluggish to real snappy, with added wheelspin and a new tendency to loop out. I liked it a lot, but ymmv. Obviously adding weight would have the opposite effect.

I'm a little surprised Alta didn't add the flywheel weight to the motor pinion instead of the driven gear; the weight could be much lighter, with the flywheel effect amplified by the reduction. I've got two Alta primary-drive covers here, looks like the top 1/2 of one could be cut off and installed on top of the upper half of the other, then internally machined for clearance. Maybe there'd be rotor-balance etc issues, idk.

 

[Philip]

We had some speculations about the purpose of the flywheel here:
Lyndon Poskitt Erzberg video