Trains, it leaks like crazy while it's running then continues probably for 1-2 hrs after saw us shut off( all over my floor)
I have 6 stihl saws, and none of the other 4 have ever done this so it's not atmosphere...
There has to be a specific cause that's common between the two of them
As they are both different saws, I would advise against assuming the same fault is common between the saws. Tho I see your reasoning.
The most common issue with the 180 is leaking from the rubber pickup / supply hose that exits the tank, and is then fitted to the supply of the oil pump in the plastic housing of the saw under the handle. Common for the rubber to harden a bit and leak there. but thats not where you say your 180 is leaking.
However as others have asked, pictures would help tell the story. maybe you need to remove the clutch and provide pictures. I had a bad oil leak from my 180, and it was due to damage to the plastic housing tearing a hole in the oil gallery, and leaking badly there, and not oiling the bar.
Again, pictures would help.
the 290 has a different oil pump and delivery hose, and again, a different animal to the 180.
do you have IPL's for these saws ?, illustrated parts lists, that will give you an idea of what parts are involved, and where they go on the saw.
I have also come across problems with where the bar seats and instead of the oil being passed into the bar oiler hole, there would be a small gap due to the base not being flat, and the bar would rock for want of better terms, thus not sealing where the oil gallery feed meets the oil hole in the bar, that caused a good leak.
Again, can you get some pictures with the clutch off on both, and we can go from there, were here to help mate.
T