John ... Welcome to LMF...
Check the carb to see that it is not in fact running fuel into the engine , washing the cylinder wall and ending in the oil... this will over a short time do a lot that will lead to big problems...
Over fills the oil.
Thins the oil allowing it to easily blow out the crankcase vent... (there is only that one)
reduces the lube at the rings causing excess blow by.
You might switch to a heavier engine oil to get a little more life from that engine, but if the rings are bad, it will not help a lot...
If you can check the compression... :smile:KennyV
PS...
As far as you know... did this engine get regular oil changes?
Hey KennyV,
Thanks for the welcome and advise. The GT235 has been maintained regularly and has been owned by my girlfriend and her family from day one.
Oil & oil filter, and air filter were changed several weeks ago, (By G.F.'s son in law, who is competent for that job), not sure what weight oil was used. The machine has seen approx. 5 hours service since that service was done. Son in law was mowing with the machine when the problem started. She started losing power, sputtering, and blowing black smoke. Son in law drove her to the barn, (Approx. a third of a mile), and parked it.
When I first looked at the tractor after the problem started, I started the motor. It stumbled quite a bit and was blowing black smoke. I shut her off and removed the air cleaner cover and filter. The filter was wet with oil and the engine side of the air filter can, and the intake horn of the carb was wet with oil. I restarted the motor without the air filter and she ran clean, (No black smoke, and smooth running). I drove it around enough to determine that she seems to have her normal power. It looks to me like the vacuum created in the air filter box, (When assembled), is sucking oil through the tube, (Crankcase ventilator?), that ends in the air filter can. Is the oil fill cap / dipstick vented? I'll have to look at that this weekend.
I checked the oil and it is clean and looks like oil, (Not thin and or watery, and didn't smell of gasoline).
The oil level was down halfway between full and fill on the dipstick. This motor has not used a lot of oil in the past and it was filled properly, (I checked it after the Son in law changed it), a couple weeks ago.
I will check compression this Saturday.
Thanks again for your welcome and help, KennyV. Wish me luck.