1) How do Rav Dimi and Rava understand the braisa of Ben Azai? Ben Azai is explained in teh gemara in a way that is clear that a margil uses 9 kavim.
2) The amoraim that explain teh tana kamma of reb yehuda do not seem to go like Rava. Does that mean that Ravin is the ikar shita?
Simcha
1) A Margil is someone who deliberately became a Ba'al Keri through Tashmish. It does not seem that Ben Azai is explained in the Gemara in a way that it is clear that a Margil uses 9 Kavim. There is one opinion that Ben Azai whispered the Heter of 9 Kavim to his students because he did not want to publicise it. Then, the Gemara tells the story about the sin that was prevented because 40 Se'ah were required. There is good evidence that 9 Kavim is not sufficient in a routine way according to Ben Azai. Therefore, Rav Dimi said that a Choleh ha'Margil requires 40 Se'ah, and Rava said that a Bari ha'Margil requires 40 Se'ah.
2) There is a rule (see Rosh, Sanhedrin 1:3) that the Halachah follows the later Amora'im from Abaye and Rava onwards. The Amora'im here who explain the Tana Kama of Rebbi Yehudah lived before the time of Abaye and Rava. Therefore, for a Halachic decision, Rava is the Ikar.
Kol Tuv,
Dovid Bloom
Can you please elaborate on what you mean 'There is good evidence that 9 Kavim is not sufficient in a routine way according to Ben Azai.' Ezra was misakein only 40 se'ah for a margil. What unroutine way would allow for just 9 kavim?
If he saw keri as a result of illness.
Dovid Bloom