Tekumseh enginge stalls and shuts down when blades start spinning

[alexanderRuskov]

I have a problem with my tractor mower. When the blades are lowered and spinning, revs begin to drop and the mower shuts off.
The traktor has 2 blades.
The engine is tecumseh, 12hp.
The carburetor is cleaned and the spark plug is sparking.
If anyone knows anything about the problem, please write.