[washington] Sold A Used Riding Mower Privately, Buyer Now Wants A Refund And Is Threatening Small Claims

Location: Washington State.

I sold my old riding mower to someone through a local marketplace for $1,800 about a week ago. He came to my house, looked it over for probably 30 minutes, started it several times, drove it around the yard, checked underneath it, and asked me a bunch of questions about maintenance.

I answered everything honestly as far as I knew. It was running normally when he tested it and when he loaded it onto his trailer.

He paid me through Zelle and we both signed a basic bill of sale that lists the mower, serial number, price and date. It doesn't specifically say "as-is" or mention warranties.

Six days later he messaged saying the mower shut off while he was using it and now won't start. He says a repair shop thinks something internal in the engine failed and the repair could cost over $1,000.

He's accusing me of selling him a mower with a known problem and says I either need to refund the full $1,800 and take it back or he'll file in small claims court.

I genuinely had no idea there was an engine problem. I owned it for around four years, used it normally, and it had never done what he's describing.

I also never promised him any kind of warranty or guarantee, but I don't have a message where I explicitly said the sale was final either.

Do private sales in Washington come with any implied obligation to refund the buyer if the item breaks shortly afterward?

Does the fact that he inspected and operated it before buying matter if our bill of sale didn't use the words "as-is"?

I'm keeping all the messages and the signed bill of sale, but I'm not sure whether I should respond beyond saying I wasn't aware of any defect.

He keeps saying he'll add repair costs and his filing fee to the lawsuit if I don't refund him by Monday.