I just sold a engine and muffler to a guy that paid me with paypal, I got the funds and have transferred the funds to my bank account, just after that I got a e-mail from RC Universe stating this guy is a scammer and not to do business with him. I still have not shipped the engine and would like to know how this guy is going to scam me once I have the funds in my bank? should I ship the engine?

Don't ship, contact paypal first, tell them whats going on, your concerns,,

What scammers do is claim the item was damaged or not as described and paypal has them send it back, once they show it's delivered back to you they get a refund,, problems is you get a box of rocks not what ever you sent.

Even using paypal as a seller you can get scammed,, I don't let new members with zero feedback buy from me using paypal,, I have them send money orders unless they have proven good feedback

good luck