ty80boy

I've just got a Yamaha TY80 for my son and was wondering what the oil / petrol ratio was? The oil / petrol is mixed in the tank and the closest guess I have is 20:1 which is what my FS1-E was, back in the day> Also, the bike would have tun on leaded fuel. Do I need to get a fuel supplement for unleaded? I haven't ridden trials since the 80s (I used to have a Bultaco and a Montesa) and so am a bit out of touch. Thanks.