Where I work I have heard comments about what a great carpenter/builder I am (this is a college theater scene shop I manage). What they don't know is how many mistakes I made to get there because one definition of a good carpenter is that he can quickly hide his mistakes.
I haven't got a build going at the moment or I would post some pics...well, I do have a pennsy A3 in 3/4" scale that I've been working on for years but haven't done anything to speak of for the last few.
As to model IC engines, the comments of many in this thread have been right on. Getting valves to seat, etc. I have never gotten my Lil Brother to run more than a few seconds. I worked on big ones and could get them going but small hit and miss I don't quite know how to trouble shoot. Is it ignition or fuel... So I putter with it a while and get frustrated and then drop it for another year or few years.
So you beginners hang in there and post and ask questions and suggest things and ignore flames. Flames are the natural byproduct of "internal combustion".
Paul (from MI, USA)