Blowing oil back through breather tube - Mtd #TB4SC 25CC 4-Cycle Gas Blower

First check your oil level. You could have too much oil in the system.

You could also have a plugged breather system and pressurized oil system, crankcase and oil tank.

If you have an air filter/breather system with rubber tubes that end over the open intake area of the induction module in behind the air cleaner, sometimes people think they should not be positioned like that and bend them back and tuck them into bolt hole areas/openings in the filter backing plate casting underneath the breather tubes look like they should have the tube ends inserted into them and it the tubes are indeed bent back and the ends inserted so, this will close the tubes off and pressurize the engine internally and the oil tank and the pressure buildup will then blow the filler plug and dipstick out of the oil tank.

its over filled or vent is plugged

There ae a number of things it could be. What it sounds like to me is that the oil is not being pumped back into the oil tank and is collecting in the cam chest. It should be blowing out of your crankcase breather tube as well if your crankcase breather tube is open. Behind the oil pump, there are three holes. One is behind and above the oil pump. This is where the breather tube from your oil tank and the primary comes into the engine. The hole directly behind the oil pump in the middle is the oil return line from the very back end of the primary where the oil from the primary is recirculated back into the engine. The bottom hole behind the oil pump is the crankcase breather. It should have a hose that runs back around behind the transmission and just dead ends in a bracket pointed towards the final drive chain. This hose should be open to vent the crankcase pressure. Have you checked to see if oil is being pumped back into the oil tank? If not, the scavenge gears of the oil pump may not be pumping the oil out of the engine and back to the tank. If this is the problem, you may not have the drive key properly installed in the scavenge gears of the oil pump. Still, oil should be pouring out of the crankcase breather hole. But, this is what it sounds like it's doing to me. The oil is building up in the cam chest for some reason.

Good Luck
steve

It sounds like the engine is badly worn. Compression is likely blowing down past worn piston rings creating excessive pressure in the crankcase which then blows out the breather tube. Solution is a used or remanufactured engine.

Blow by is what causes it - Those motors weren't really designed to be turning RPM's all day. You will want to install a oil catch can inline to help pull the oil out of the breather assembly. There is no way to stop it unless you upgrade to the newer XB PCV breather setup.

that would be the rislone

You either have a head gasket going bad or your piston rings are shot which causes air to go down into the crankcase building up pressure which exits through the breather tube.