If the previous owner had used a quality synthetic oil based fuel the engine would be like new , inside and out.
I'm sorry but after running all my engines on this fuel
http://www.westonuk.co.uk/index_045.htm for the past 5 years I just don't subscribe to the castor oil is best debate.
The engine might be ok for a hack model, but it looks like it's done its best for its previous owner.