Question on a 109 metal lathe.

[buster]

Hi,folks... The main drive pulley has a gear on it and one side is wallowed out big time.It goes in between 3 gears of which I can see no need to be there as they don`t do anything. Can I put a regular step down pulley on it or do I have to stay with the original setup?

Any help appreciated,have a great rest of the week and thanks,buster