I do not have any experience with this 2-stroke 100cc Suzuki bike, but what you describe of the problem I would serious check the exhaust pipe. With 2-stroke motorcycles you need to clean the exhaust system several time per year, depending on how much you use the motorcycle. I would recommend cleaning the exhaust pipe, and muffler twice per year.
I have a 1984 Suzuki GP100 which is running badly. I have cleaned the carb and jets and checked the plug. It has a CDI fitted. It ticks over fine, is very sluggish up to 5,000 rpm but fine over that to the redline. The airfilter is clean and the spart looks fine.Does anyone know what I should look at next?