I had bought a 1975 MX 125 for my youngest son. It was a surprise and boy was he. After a couple of times riding this vintage bike, my wife suggested that I too should have a bike to ride. So I bought a 1974 Enduro 400 Yamaha in a box. Once the beast was together we rode all over the place. It soon became apparent that this 400 was a little harsh on the old back (43 years of abuse). So I was on a parts quest for the MX 125 and found a man with a bunch of old bikes and parts. He also had a YZ 250 in back, that was for sale. $100.00! I thought to myself, I could fit my Enduro motor into this frame and have nicer suspension...... So I came home with parts for the MX125 and a new project! This Frankenbike (endurograph) was a beast! It was also identified as 2X5 or 1979 YZ400 not a 250.So time goes on and I am looking for something a little more dependable, when in the in the Cycle Trader is an add for a 1980 YZ250. Also stated was a list of 1978 400's and a 79 YZ400 from the same seller. So I met this guy, Eric, who is a 1978 YZ400 enthusiast! He has a 79 YZ00 in parts laid out on the floor. There is a new Wiseco piston and rings. So I bought the bike in parts and scheduled a bore job for the barrel. Eric assembled the engine after inspecting the tranny and crank assembly and replacing all of the seals. But when timing the engine, Eric found there was no SPARK at the plug! Now I am looking for a working stator. I am searching the internet and salvage yards looking for the illusive stator. I receive an e-mail from Bill Johnson of Vintagemotocross.biz, who says he has one. Nice! We make arrangements, and soon I have a working stator. Now, as seen in the picture on this site, I start putting the bike together. It was like an ugly duckling at first, but as I could add things like decals and DID chain and sprockets etc...The front forks are from a 1982 YZ490.
The double leading shoe is a bugger to adjust, but I am getting closer.
I have recently added a DG pipe... Boy...what a difference! I have been running "Race Gas" to prevent any detonation.
I have been racing in the local vintage mx circuit, and having lots of fun. The bike is great....my skills are less than great!
It is amazing as to the power this thing has! Role the throttle on, and hold on!
I hope you enjoy looking at the pictures of the evolution of the old YZ400.
     On the Vintage Pictures Page, I have some old pictures at the Washougal MX Track back in 1975 when I was a youngster racing in the mud. I rode a 1975 Honda  CR125 back then. I raced At Delta Park, Washougal, Woodland Winter Track, Castle Rock and down at Fox Hollow. It was a lot of fun for me. Some old pics of me on my CR125, a pic of my youngest son on his MX125, and Eric's 78 YZ400E "A Bike"
      I am always looking for parts for the 1979 YZ400 2X5 and YZ250 2X4 body parts work too. If you have any and looking to get ride of them, e-mail me @ evolutionyz@iinet.com. Thanks and Enjoy!