Fuel In Engine Oil

Welcome mate, have you checked the float heights after the carbs have been fitted and primed with fuel?

 

Sounds like your new float needles aren’t sealing when the float bowls fill with fuel?
Could be a fleck if dirt on one of the seats or could be the float level is too high or even a float is not floating?
Best of luck resolving it
Taff

 

I had a similar issue with my '98 TBS.
I believe that they're the same engine (?).
I was told that it was when on the side stand the fuel in the carbs would drain to that side and flood it, I had fuel dripping from the air box.
The solution was to shut off the pet cock and let it run for a bit, to drop the fuel levels in the carbs, before parking up.

 

I have seen porous floats that will gradually fill with fuel and thereby keeping the needle valves open.

 

There's an o ring on the outside of needle seat insert. This can crack or harden and shrink which the allows fuel to seep around the outside of the seating and into the float chamber causing it to flood and run into the motor giving the problems you describe.
It will also cause over rich running.