I currently have 10 Honda ATV's in the yard. 5 of them are mine, the others have been left for me to fix. Needless to say the Jeeps are being neglected.
Anyhow, I've really found it interesting looking into these engines, and so many parts remain the same, but have different part numbers, For example, a crank from a 2007 420 Rancher is $100 more than the crank from a 2012 420 Rancher. Parts are identical, but have different part numbers.
Anyhow, in doing some nosing around in parts schematics, I discovered that the cranks on the 420's and the 2012-2013 500 Foremen are the same, and sure enough, you can swap a 500 top end on a 420 bottom end, add fuel (programmer) and you have a 500 Rancher.
Soooo, just rebuild a Rancher AT (automatic) for the wife. Did an 18% gear reduction in it (stock secondary gears from a footshift Rancher), 500 top end, all using stock Honda parts. She'll have a 500 with lower gears in the little Rancher frame. Should be pretty sweet little rig. My buddies said I need to take out a term life policy on it before she rides it (she likes to go fast).
Picked up a 420 footshift last week that needs an engine rebuild. Will use the old 420AT cylinder etc to fix the footshift and resell it. At least parts for these are cheap and I can pull a motor and rebuild it in a day, unlike the Jeeps.