This is an excellent model. It is obvious how it goes together, the instructions are simple to follow, the parts were crisp and we had none of the "timing belt" problems some people have mentioned. Quite the reverse, in fact it worked perfectly first time. "We" are my son - not yet 5 and me. He got such a buzz out of us completing each stage it has made me start looking for a similar project. No, at his age he cannot fully understand how a combustion engine works and he has the attention span of a gnat at times, but who cares? He does understand the mechanisms of cams, belts, cranks etc and is trying to use some of these ideas on his own with his lego, so what he did learn stuck. Most of all though we had fun together building it -what more can a parent ask of a kit like this?
The biggest drawback? It's loud. He often wakes his little sister by firing it up after bed time!