On Mototassinari’s website Beta (and Sherco) are no longer listed. I emailed them for parts numbers as I want to replace the reeds on my 300 and they sent me a part number which I was able to cross reference. The part number for the reed block assembly is V417A, reed petals are 4P672H, and gasket is G316. Attached is the link from the MT website.
Garrett
http://store.mototassinari.com/app_vforce4_moto_atv