Dear Richard,
I completely understand how it is and I really LIKE this little kit.
My personal opinion is that replacement of any small broken part due to modeller's mistake is not required. All those can be easily replaced by few bits of wire and anyone capable of minimal scratch building should be able to replace them.
Maybe think of one additional image, posted on the website and showing which parts of the engine goes in that or that hole in that or that order would be enough. It is a common mistake to create something completely clear to yourself and everyone else involved in the project, but kind of vague to "outsiders".
As i said the bike is completely buildable fir a newbie to resin like me and I really enjoy it!
Keep up the good work Aviattic

Best regards,
Sasho