TOPIC:

I'm sure it's been asked before here but can anyone tell me what this is for welded to the frame/chassis?

That post is for a factory option cable lock. I have seen them on several different models but it seems to be a European option.

Have you got rear foot rests? On 900's there is a "hoop/bracket" that the rear pegs are mounted on.
Seen many a bike with them cut off. Webike even do replacements for 900's it's that common. 
Or maybe as injected mentioned below for cable/chain. Obviously kawasaki thought us in Europe are not trustworthy and spend all day going around nicking bikes that aren't chained up. 
 

It's for the optional cable lock and common cause of the lower frame rail rotting out due to water ingress if left with the sealing cap off.

Yeah have rear footrests 

wrote:

Have you got rear foot rests? On 900's there is a "hoop/bracket" that the rear pegs are mounted on.
Seen many a bike with them cut off. Webike even do replacements for 900's it's that common. 
Or maybe as injected mentioned below for cable/chain. Obviously kawasaki thought us in Europe are not trustworthy and spend all day going around nicking bikes that aren't chained up. 

 

             Kawasaki were right! In Leeds where I grew up there was a group of bikers you could loosly call a "Patch Club" , One of their revenue streams were the sale and manufacture of steel cable bike locks.I was asked by them if I wanted to buy one for my Bonneville.  I said I did and they asked me for my adress so they could deliver it to my house as they were made to order. I commented that they must have something big to cut the cable to make it into a suitable length for a bike lock. It went quiet  and they stared at me a bit......I said I'd changed my mind.