Here's another possibility for your failure. Worn out timing chain guides. While it would be unusual for the guides to be worn enough to jump teeth with only 12,000 miles, it's not out the question. Here's why. The links on a timing chain and most all chains, for that matter, are stamped. If you pull the chain out of your broken motor and look at the edges of the links, the part that rides on the guides, with a magnifying glass, you will see what looks like a metal file. This is the results of a badly worn stamp press. Whenever I replace a timing chain, in any kind of engine, I first take it to the polishing wheels and polish the side that will contact the guides until it looks like chrome. Harley Davidson (sorry Tom to mention that dreaded name and I use it here only for illustration) has had a world of problems with their cam chain tensioners on their big twins for this very reason, resulting in class action. Perhaps your engine was built just before they replaced the stamp jigs. Anyways, I'm sorry your engine broke and I know Kymco makes quality bikes.