I'll need to convert it but if I remember right it's a fine threaded 8mm bolt so about 40 to 60 in/lb should do, this nut is fairly thin compared to what it should have there so getting a wider nut from the hardware store will help ensure it doesn't strip out. Mine stripped out but that was from using a cordless drill to crank over the engine and run a compression check after I built it. Using a wider nut with more thread contact fixed that problem too.
For the factory nut tho, since there's really not enough threads left on the shaft to use a lock washer, use a few drops of Green (low strength) locktite on the threads or use blue if you can't get the green, just don't use red.
I got a fine threaded nut (M8x1.0) from an auto parts store which is about twice as wide and can withstand normal torque much better than the one that's on there now.
Basically go 30 to 40 in/lb and low strength locktite if using the factory nut, or go 40 to 60 in/lb and medium strength locktite if you get a regular thickness nut from a hardware store or auto parts place like pep boys or autozone.
Some thread lockers (locktite) from other companies use purple for low strength and some are green... just another tidbit of gee-whiz info if you see the purple stuff and can't find the green...