Ok. So in November, we sold our ATV to our teenage neighbors. Other that a wonky CDI, the bike was running fine. We just weren't using it. It is a 2013 with 3200 km on it, sold it for around $1000 under list because it needed the CDI and a rear master cylinder, and the tires were around 1/2 worn. They hounded us for weeks to sell it to them. 2 days later, the kids informed us that the engine crapped out. They put on a good CDI, and changed the oil before the engine died. The engine was a warranty replacement around 8-900 km ago. Also, the bill of sale stated as is, where is, with no warranty implied. I think they used the wrong oil or didn't put enough in, and was sold as is, but my wife feels guilty. What would you do? Their mother called my wife today just to say the engine is gone. We're not sure what to do.