Is there any chance of a pic of the air filter, you have me curios now, as the V61 did not have a hi-zone filter (4-stroke) and therfore i did not think there would be an air filter sticker for this one out there!
What you have is a V59 1969-1970 160cc Special, well yousrs specifically is 1970, it has a Series 70 MKI Engine, and a G3 carburettor, with no decompressor on the cylinder.