I have an '88 Blaster. FMF exhaust with silencer. Stock carb. Oil injection blocked off. Premix 32:1. The problem is running way too rich. Gas is actually getting pushed back into the air cleaner. Have tried to adjust the floats with no results. Carb rebuilt. Compression is good (120 psi). Reeds have been replaced. Spark plug is slightly black, usually wet. Anybody experience something similar? Any help would be appreciated before I take it to the shop.