Oil for 73 t140v

Hi folks. Joined last night and a new proud owner of a 1973 bonneville t140v.

Wondering what is the best oil to use?

Also any idea how to fix the speedometer and rev counter? They bounce quite bad while riding.

Cheers
Tiger

 

Thanks for more info and adive chairi1. Cleened out rev counter cable earlier, just letting all the dirt drain out. If that works will do the same with speedometre. Cant start bike up at the moment cos my b

Cheers steve!

 

Is that semi synthetic?