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Take the blower hpusing off and run the engine for a minute or two .
The source f the leak should become obvious.
UT will not hurt to run the engine for a few minutes without the housing but not for long enough to mow .
You might need to push the dip stick tube down if it is held in place by the blower housing./
Prime suspects are the dip stick tube or cap , top oil seal or counter weight ventilating the crankcase .
Lower down is a blocked breather tube or split breather .