Hi Cello, I have 3 Techno's and all 98 black models.
Carbs can be an issue especially when leaning the bike over at sections, unless you turn the petrol off. The Mikuni's Vm 26?? are hard to source spares for (I needed a carb top and looked for ages).
I'd suggest buying an OKO copy carb off flea bay, (around £30) and try it.
As for the float height, I set mine too the manual, floats around level with the carb body, also attach a pipe and with the bowel off simulate its correct position, and manually work the floats to ensure the needle valve stops the fule supply.
Best of luck and keep at it, as the Techno's are a great bike and still competitive.
Jim.