Clutch Service Advice, Please Help!

The "Clutch Boss" in the center. It is the LAST thing standing in my way of riding, after a self done overhaul. The Bike is a '97 YZ125J1. I need to get in there to pop out the basket in order to file down the grooves. Unfortunately, the factory manual doesn't tell me the NUT SIZE of that middle "clutch boss" nut. Does anyonr know the size, or a better tool to use than a rachet to take this nut off? Any other advice with the plates or the basket? It seems to be on there really tight, has anyone else had this problem? It isn't reverse threaded, is it?

Sorry about the 20 questions, it's just that this is the LAST thing standing in between me and Twisting some throttles! Everything has gone ver well in the self overhaul, I'm just stuck here... Thanks in advance for the help! :)

-Sterling

Cool. Thanks a lot for the advice BigRed. I'll pick up the proper ratchet size tomorrow. I don't have a clutch holding tool, but hope fully I'll still be able to get it free. I'll have to think of something. I MUST RIDE! :)

Bought the 30mm, it is TOO big, They didn't have a 27mm, so I bought the 24, TOO small! Can you believe it? UUGGHH!! I am not looking for a 27mm, will check Sears tonight. How much is a clutch holder tool? Has anyone ever done it WITHOUT this tool? I don't have it, hope I don't HAVE to get it. Thanks again for the advice.