You are almost certainly correct about it being in Cycle, not Cycle World.  When I was a kid I used to pore over old copies of one of those magazines in the reference collection our local school library.  The collection was pretty small, but I learned a lot, and read about a lot of cool stuff from before my time, like TT500's bored and stroked to 716cc, stuff like that.  I liked the fact that they always published dyno results of new bikes.

"79 YZ400F had a longer stroke & 82mm bore--one year only & was lucky enough to get one new. Was a great model but then replaced by the YZ465G--& the world changed lol. The F may have had a shorter rod to keep the overall height of the motor the same as earlier years with the 85mm bore. But i'm only guessing.

Cycle, March 1976.

Have a look on a South Africa site called motorcyclespecs

hi,

i would like to see this project get done as i have done a 250 dt to yz, and i also have a dt400 sat in the shed waiting for the day!

go for it, so worth it.

cheers
les.

It's been done more than once.  Here's one of the threads.

yamaha-enduros.com/index.php/forums/rest...ject-the-super-dt400

thanks Mark, just finished reading the whole thing, very inspiring.

les.

What a numpty I am! The Cycle article we were talking about is right where I saw it a few days ago, on this very site!!

yamaha-enduros.com/index.php/articles1/a...8-76-yz-400c-article

Under the "tech library/vintage articles" tabs at the top of this page.

"What a numpty I am!" 

Numpty, a word picked up from 'er indoors by any chance..........?! 

Not a Yank word, must be one I picked up either in Oz or Blighty. Think I've heard my bruvver-in-law use it.  You'll get a bit of an odd form of the language from me, I'm afraid.