Recently I bought a 2013 yz250 with only one owner from new which had been sat in a garage for over 2 years due to injury. The bike came with the full spares kit! I began stripping the bike yesterday and found it was fitted with a vertex piston, which got me thinking why would someone put a vertex in there when they have a genuine top end kit sat there? The piston fitted was a size A (66.34) even though the cylinder is clearly stamped with a C, and the piston in the spares kit is green (66.36). I'm guessing that's why the piston looked like this when I removed it......