What is this called ?

[Buckybriggs]

this was on the end of a shaft extension off a 4 stroke 110cc or 125cc automatic with reverse
Also looking for a new shaft . It's like a Jack shaft . The go kart was given to me to fix up for neighbor boy. I can't find one I have a welder I'll just modify a jack shaft and and do it that way but if I if I could I just rather just buy the shaft in the bolt and the sprocket and just put it all together

 

[Whitetrashrocker]

Never seen that on a kart. Looks like it was someones genius idea fix. What's wrong with it? Looks like you can open it and I bet it's just 2 bearings and a shaft.

 

[Hellion]

The go kart was given to me to fix up for neighbor boy

Show us what you're working with.