I would made him pay for a brand new one. Either that or take the cost out of the paint on one his prised possessions.I let a guy use one of my chainsaws once because he assured me that he'd been the the "Stihl Training Academy" and knew all about them, blah, blah, blah. First off, I've never seen a display of "not knowing **** all how to make a cut" like he was doing, then later, when it got strangely quiet where he was working, I wandered over to see what was up. He had the damned thing taken apart claiming it needed "adjusting." WTF? Then, it wouldn't start/run after he reassembled it. I took the cover off and found he'd not even got the chain back onto the sprocket under the cover. What a ****ing disaster. Never. Again. **** up your own shyte, leave mine alone. I don't care where you graduated from.
If someone takes something like that apart they are assuming all responsibility for that piece and price of said equipment. PERIOD! You break it you buy it. No negotiation!