Did you post this elsewhere ?
I am sure that I have already answered you.
However I will di it again just in case I am going bannanas.
I have several 2000 series Cubs in my repair run and all were "overheating".
Some had removed the side covers from the bonnet but it made no difference.
I found the real problem quite by accident when one of the fuel pumps failed.
There was not enough flow from the tank.
It ended up being a plug of debris in the outlet from th fuel tank that was not enough to stop the flow, but enough to slow it down enough to cause the engine to occasionally cut out.
When we removed the offending tank there was a mounding fin inside the outlet hole which was creating an anchour point for the debris to accumulate on, so I ran a drill then a file up there after cleaning out the tank.
Did the same to each & every one when they ame in for regular service.
All had a plug in there and none have had a problem with "overheating" since.
Having said that it can be genuine ovrheating and proper cleaning of the engine is difficult as you can not easily remove the engine cover due to the flywheel PTO shaft.
If you go blowing a lot of air down there please remember to pull the choke on hard or you will end up with a carb full of dust the blow it off before opening the choke.
Better still is a rag down the carb throat.
Be careful with the choke linkage as the plastic spring loaded connector will be quite brittle and the cap is not available except as part of the choke rebuild kit ( $ 60 )