A while back, Enduronut was kind enough to sell me the actual YZ-465G I had when I was 14. Earlier this week, I obtained the actual DT-400B that my older brother had when he was 15. It was in a small town about 25 miles away. The guy that had it works at the same company that I do. His brother bought it from my brother in 1978 or 1979.
It sat outside under an awning for years and is in rough shape. The guy just gave it to me. Well, I knew he likes blackberry brandy so I brought him a bottle. (-:
It is locked up. I was curious so I pulled the head and cylinder off it tonight and it doesn’t look good... )-: It appears that the piston exploded - pieces of aluminum everywhere!! The rod is bent and I can’t even find the wrist pin!!

Man, what a mess. My guess is the wrist pin would be all those little pieces rattling around down in the lower end. Imagine what it must have been like if someone was riding it when that happened. I recall driving a school district van along the interstate when it threw a rod, and that was not pretty even though I had four wheels under me and a cage all around me.
Two ends of the spectrum: Enduronut's perfection and now this...

I love these stories and it doesn’t usually work out for most, yet you are two for two! Hopefully you can save the case half with the numbers and the frame. All else is just parts on your Brother's bike. Good job!

OMG it's amazing what can happen in there. Keep the cases if matching VIN to the bike and build it up from there. Everything is available from one source or another. I built my 76 DT400C up by splitting the cases and replacing all bearings and seals. Crankworks out in Arizona can rebuild and balance cranks. Good luck with your project...cool story too!

Wow--just wow. Seen a few blowups but that's right up there with the best [worst]. & a 465G at 14--arm stretchers those.
Ha, had me dreaming about mine back in 1980 & then realised it's in my avatar.