10W40 mineral oil good quality will do the trick. in the UK.
The 10 means the lowest optimum temp, W means winter, and 40 is the highest optimum temperature so if you live in a hot country then use a higher temperature oil and like wise for the winter.
More important is to use a good quality 2 stroke MOTORCYCLE oil as on 2 strokes this is the area that can go wrong.
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Honda nc23 CBR400 AERO 1986, 1990 honda NC23 Tri-Arm, 1987VFR400 NC24 Rothmans Rep, NSR250 MC16 1987, CL250s 1983. Moto guzzi zigolo 110cc 1958. Fantic 50cc 1972. Suzuki Cobra Race bike 500cc 2t 1975 , GP125 1975. Triumph T110 1954. BSA Thunderbird 1955. Ariel VB 600 1952, 1990 MuZ 125 etz.