I have a 17 hp Kohler twin on a QT 17 that is blowing tons of oil out the crank case breather tube.. is there a valve that goes bad on these ? The engine was rebuilt 5 years ago and I would guess has 200 to 300 hours on it .. Thoughts ??
Check that the dipstick seal is sealing properly. Then check oil level. I think this engine has a mechanical powered fuel pump, it may have a leaky diaphragm sending gasoline into the crankcase. Same with vacuum powered fuel pumps. When the oil level gets high, it'll send oil out the vent.
And yes, if the reed is bad in the breather assembly, it can cause this too.
The breather valve sometimes malfunctions on those engines causing this problem. i have a series 1 on a JD317 that was soaked with oil when I got it. The PO described exactly the symptoms you have. Try removing the breather cover and see if the plate and valve look Ok. I ordered a new one for mine but haven't gotten it back together. Excess carbon buildup on the head and piston can also cause blowby. The carbon eventually interferes with the piston at the top of it's travel and unseats the rings causing blowby. I had this problem on a single cyl K321. Removal of the carbon solved the blowby problem in that case.