Anyone know the axle nut size? Size of the threads that is on a 250 sx

[Don 86 250sx]

I headed out today on my new to me 250 sx, 86 year, into the Ocala national forest. The ride got rough, like a wheel was gonna come off. Sure enough, the axle nut came off and is gone. Does anyone know the thread size? I want to try and find a nut locally while I am out here, doesn't matter if its not a castle nut, I will double nut it or use locktite. Just don't wanna blow the whole 2 hour trip out here. I guess the PO didn't put a cotter pin in it.

[Chopsaw]

250 SX threads into the lower shock tube . There is no nut .

[El Camexican]

Rear nut is 18mm, but I have no idea what thread it would have. Good news is that P/N 90304-HM5-A80 is still used by Honda. Any Honda dealer should have one on the shelf.

[Don 86 250sx]

I found out its 18mm fine thread, no hardware store has it. Found a local Honda dealership, kid at the counter is younger than my bike, walked him through it, not in stock. I ordered it from Ebay.

[Chopsaw]

Sorry , for some reason I was thinking front axle .