A couple of months ago, I acquired an OS 48 Surpass from a guy in California in exchange for a new in box TT 50 heli engine (genuinely NIB, I had not removed it form the box). I laid the engine aside once I'd got it, waiting for me to build my 4 Star. Now I've finally finished the model, I have found a few things wrong with the engine, first that the mounting holes have been filed out, but more seriously, the cylinder head is a right-off. The rocker cover was fine, but I removed it to adjust the valves and found that the front mounting screw fell out after one turn. The lug it screws into was cracked. I then found that the casting that the cam gear pivot is fastened to is also broken, though an attempt had been made to fix it with epoxy (!).
I now have to replace the engine (don't want to spend that much on a small engine), try to find a new head (out of production/stock everywhere I've looked so far) or abandon the model I've just spent 6 weeks building and covering.
The lesson I've learnt? THOROUGHLY inspect second-hand goods at the time of purchase!
I sent some pictures of the damage to the seller, but have had no response.