Z550 problems

There was a guy on ebay selling Tk22 parts and he had them broken down to each individual part. You might be able to get a jet holder from him. Be aware, the jet holders on TK26 and Tk27 carbs look similar, but they do not interchange with Tk22 carbs.

But with so many issues, you may save money in the long run by getting a full set of Tk22 carbs.

To be brutally honest, those carbs are F**ked up, don't use JB weld that would be a botch, the screw in the breather pipe is probably just plugging that particular stubb as it was most likely the Vac take off for a vacuum petcock, find a decent set of used carbs there are plenty about and will be cheaper in the long run. the previous owner was no doubt some sort of retard.