Wow, only 50 ?
As deep and thorough as Mark's knowledge was, I thought that some of it was from having been there during the mini bike golden era of the late 50's, the 60’s, and early 70's. Watching the Sears, JC Penny's, Popular Mechanics, and Boy's Life ads, as they came out with each publication, each season.
If Mark was just 50, that means he was born around 1973, toward the end of the era.
That means Markus learned all that mini bike information post the era, and was learned from observation, research, and hands on experience.
That makes his story even more amazing !