Sandcast 4286 is listed on ebay with E371. Seller says he acquired the bike with a K1 engine and put in E371. In the VIN directory, 4286 is listed with E4991.
It looks like a very nice restoration.
http://www.ebay.com/itm/Honda-CB-/331539934633?forcerrptr=true&hash=item4d3151eda9&item=331539934633
Thank you, Kevin. I wish I could say I'm 100% satisfied with the bike, or that it was as nice as so many of the restorations on this forum. I have to sell the bike, now. Time and money constraints have forced my hand despite a few things I wanted to fix, and even a few things I didn't know needed to be fixed, such as the fork top bolts. Although the frame was listed with E4991, it had a K1 motor, and very few usable parts when I bought it a few years ago. I regret not having the head fins fixed, among a couple other choices I made along the way. I spent a lot of time trying to get the finish on the clear coated parts right, but they came out wrong. The still looked nice, just not exactly right. I would never claim it's a museum quality bike.
As I conveyed to Gerard in a message, perhaps I should have asked for more guidance from this forum during the course of my build.