It'll work...
My RT1 uses a YZ490 set up and its all good.
I had to weld some "tabs" onto the stator plste first, then stick thst in the lathe
to get it to fit the RT1 case.
Then you csn measure the distance the flywheel is from the stator plate
and then remachine the taper to suit.
Mine no longer has the keywsy and its never been a problem in the 3~4years
Its been on the bike. Obviously make sure its lapped on well.
Cant remember how many mm BTDC it is but around 3.2 rings a bell.
YZ490 flywheel weighs 1450grams
Cheaper than some of those aftermarket set ups and still Yamaha