EGT became high after carb cleaning

"WOT 5890RPM on the ground".

The issue is most likely the carb maintenance since it wasn't an issue before the carb maintenance. A fully air exposed engine usually runs a little cooler than a cowled engine. Oil and CHT's are a little different than EGT's. EGT's are more influenced by fuel. Your problem sounds like it lies within the carbs since they were taken apart. Just a side note*** 5890 on the ground is way too high. (ground adjustable prop)  A static WOT run is usually around 4500 - 4700 depending on the type and size of the prop. I found static different between 2 and 3 blade props in my research. Static rpm just gets you in the ballpark. A WOT run in flight will help you fine tune your prop pitch. Try and set the prop to get around 5600--5650 rpm WOT in level flight at your AVERAGE altitude. Pattern altitude may not be average depending on your habits. If you want or need a better climb prop over a balanced setup then shoot for 5700-5800.

Watch your oil temp and make sure they are in the normal range. The EGT's can be adjusted IF necessary by moving the clip on the carb needle. Double check and see if the needle clip is in the #3 slot from the top down. This is stock and should be fine. Make sure the mixture screw on the bottom is set at 1.5 turns out.  

The only other thing that I can suggest and I may be totally wrong is that the needle jet on one or both carburetors was inserted upside down. I don't know if it's possible to screw in the main jet with needle jet put in the wrong way. It's been a while since I disassembled a Bing carb. The needle jet is a brass colored part with one end very small diameter and the other large diameter. According to the diagram the small end diameter of this part should be going through hole first followed by mixing tube with o ring, shim and finally main jet. 

The hole above ball where the last item is main jet screwed in. Before main jet first item is diffuser, second needle jet, third mixing tube where there is slot for the o ring, fourth a shim and finally the main jet. All parts must be inserted in order, right direction and not missing. The o ring must be new or not damaged or twisted when inserted. 

The jet needle is the part that looks like a big needle where you put circlip in third position. Top most position is lean. Why they named the long needle part jet needle and the other part needle jet I don't know. 

The o ring before main jet could have been damaged if it came in contact with volatile cleaning fluid during cleaning. 

Hope your problem is resolved and look forward in hearing a resolution. You did mention something about mechanic replacing nozzle. Do you mean the main jet since I see no part listed as nozzle in Bing manual. I may have misunderstood or wrong. 

Bing has in internet a free download manual with diagram, and number parts. The manual has a blue cover. 

I had mentioned before that first item in hole where final item is main jet is the defuser. Another AKA name for defuser is that it is the atomizer. There is the possibility that it may have been damaged or microscopic hole somehow became enlarged during cleaning or insertion. Perhaps if new ones, same part number as before, is replaced may solve your problem.

Hopefully nothing that required being screwed in was not cross threaded since very careful measures and correct tools must be used without distraction and patience. 

When you say he "opened the carburetors for cleaning and testing", what did he actually do?  It sounds like he disassembled them, but why?  Were they due for an overhaul?  Does he have have experience overhauling Bing carbs? 

Tyler Hathaway wrote:

When you say he "opened the carburetors for cleaning and testing", what did he actually do?  It sounds like he disassembled them, but why?  Were they due for an overhaul?  Does he have have experience overhauling Bing carbs? 

Just regular testing and cleaning..