ok,,,these little beauties are "the Bling" when it comes to lighgtened flywheels, without costing an arm & a leg for a full steel job,
I did my first one when i was about 16 years old & i still have it in my race motor to this day, (working that out it`s now done approx 26 years of Mad Matt abuse, that would be about 500 years of "normal" person abuse

)
i can`t count how many of these flywheels i`ve lightened & not one has given any trouble """EXCEPT""" for one guy who simply didn`t know what he was doing when setting it up & he got the centre all cocked up, flywheel still didn`t fly apoart, just simply wobbled, a friend of mine bought it off him for $20 & has since re-centred it & is now in his 1470cc turbo motor
Ken nelson , Fred Sayers, Henry Draper, My dad, & soooo many other people have bought thses flywheels & still no problems,,,i`d "guestimate" that approx 300 plus of these flywheels are out there in the mini world.
They are all CNC machined, that is,,,we did the program to run em & now days we just bolt em down, centre them & hit the go button,,,all of em are exactly the same cutting
easy-peasy
My race mini saw 9000rpms quite regularly at speedway from about 1982 to about 1988, that`s a lot of revs , for a long time, in a very hard yakka type of racing, nearly every saturday nite, then it did a number of years on the race circuits up here, Lakeside, Morgan pk, Willowbank etc including all the hillclimbs & autocrosses that i do & then it hit Targa Tasmania for 2002,,,you just won`t fault them simple as that,,,they remain quite thick, no "thinning" down at all,,,just CNC machined out 3 big scollops & then another layer of 3 big scollops
finished weights depend on the original flywheel used,,,there are quite a few different castings, some thicker than others to start with, but generally a finished flywheel can end up at about 5&1/2 - 6 kgs
i personally use the competition steel back plate,,, but we set these up for road use as well & a std back plate is quite ok
they cost $150 "EXCHANGE" for your std "2 Piece" flywheel...
I WILL NOT LIGHTEN THE LATER STD ONE PIECE ITEM!!!!!!!!!!!!!!!!!!!!!!!!!!!!