"Technician claims intake tube from air filter to carb was dirty causing oil contamination."

I have never heard of such a thing. Most likely the carb. float needle stuck and allowed gas to contaminate the oil. Don't know WHAT tech you talked to, at the dealer where you bought the mower or a B&S Field Rep. In any case, I would send registered letter to B&S. I have been told by GM Dealers a couple of times that they were not going to do anything but they found out they would.

Keep records of all phone calls, correspondence, the nature and results of these. Don't know what state you live in but check if your State Att'y General has a Consumer Relations, Consumer Fraud, Division. Local Ford Dealer found out he could do something after selling our son a reconstructed wreck without telling him.

Walt Conner

I would go there and ask to see the engine in its disassembled state.

Dirt ingestion will cause cylinder and ring wear as well as oil contamination. But, I doubt that you would damage enough in 170 hours to cause a mechanical failure.

The most likely cause of a broken connecting rod in a dirt ingestion situation is from lack of oil. The rings will wear and start letting excessive oil by. The oil level will drop and the connecting rod and bearings will overheat and fatigue.

Can you prove what the oil level was when the connecting rod gave up?

The shop must keep the old parts until the end of the transaction (and longer if the parts are deemed to be covered under warranty). They also should have drained the oil into a capped container and saved it. The collected oil would speak volumes as to what went wrong.

Walt's recommendations are also very good.