I also posted this in the garden tractor forum, but thought someone here might have a theory.

A few weeks ago, I was mowing winter weeds & picking up leaves with my Craftsman ZTS 7000 (Briggs & Stratton 21hp Platinum Series) and noticed a little blueish smoke. After about 15 minutes of mowing it let out a big puff of blue smoke. I immediately headed to the garage to check it out. I noticed oil on the deck under the carburetor and it appeared to be coming from the fuel pump. I called Sears service and scheduled an appointment.

Fast forward 2 weeks and the Sears service tech showed up. We discussed the problem and he diagnosed it as a sticking needle in the carb, causing gas to flood the crank case, causing oil to be forced into the combustion system. He replaced the carb and fired it up. Unfortunately, it's pouring rain, so he let it run on the carport for a few minutes and called it fixed.

A week later it dried out enough for me to get back to mowing and within 10 minutes it sputters and let out a HUGE cloud of blue smoke. I parked it and there's oil dripping from from a hole on the fuel pump again.

In conversation, while replacing the carb, the tech mentioned that sometimes on a sloping yard like mine, the mower will "vent" oil from the crank case into the combustion system when the carb is on the downhill side of the slope. I take it back out on the yard and test it. Sure enough, on even a slight slope, it smokes. On a bigger slope, it sputters and fogs the neighborhood. During my short test run, the oil level went from full to about 1/8" below the add mark. We're talking maybe 10 minutes of total run time.

I bought the mower mid season last year, mowed the yard every week and used it to bag leaves all winter on my sloping yard with absolutely no signs of oil use or smoke.

Sears is scheduled to come back out next week, and I wondered if anybody here has any theories in case he can't figure it out and tries to tell me it's just the crank case vent. Why would that have just started & what can I do about it? I've got a 1 1/2 years left on the warranty & need to figure this out. Obviously, I can't smoke out the neighborhood on every mow.