Studs in front and back are 6mm, to remove them you will need to double nut each of them, to do this you take the nut off of each front stud, thread first nut on stud down far enough that you can thread the second nut on and up against the first one you put on, now you will need one 10mm wrench and either a second 10mm wrench or a rachet and 10mm socket, put wrench on first nut you put on stud and put socket or other wrench on second nut you put on and now turn them toward each other so that they lock together good and tight, now put your wrench on the nut closest to the engine and turn the wrench counter clockwise, this will back the stud out, then loosen the outter nut from the inner nut and repeat the process on the other one.
As for oil for mixing with the gas just use a quality 2 stroke oil like you will find at napa, autozone, advance auto, OReilleys auto parts....ect. dont buy the oil designed for outboard boat engines like quick silver, evinrude.
penzoil, valvoline, royal purple, Lucas, yamalube, maxima, and several other oils will be fine as long as the oil is a good quality oil designed for air cooled engines and I would mix it at 32:1 ratio.
Not sure if this answered your questions completely but I hope it helped.
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