Cleaned off the bike today and confirmed there’s a bow about the middle of the rod. Need to pull the rear wheel and check the shoes.

Over the past two weeks I’ve done over 60-miles off-road on my ‘79 YZ400 and I have to say this bike continues to impress me. Truth is I like riding it more off-road than I do on a motocross track. Whether I’m lugging the motor or have it on the pipe it just continues to pull and it’s perfect in open terrain.

 

 

 

Man you do great work. Question though although i might've missed it--"79 YZ is 82mm one off long stroke motor 2X5 piston & IT400 stayed 85mm all the way as did all other YZ400 before "79. So did you bore it ok to 85 without bringing up alloy anywhere. Tried going to 85 on my 360 & alloy appeared bugger it. I use the 2X5 82mm in my early 360.s when i have to go out past max yamaha 81mm.

Just like the YZ, the '79 IT400 went to the 82mm bore with a 75mm stroke. Both bikes use the same cylinder. In '80 the IT went (back) to 85mm with a 75mm stroke making it a 425 whereas the YZ increased both bore to 85mm and the stroke to 82mm making it a 465.

Cool thanks, good info. Yeah i had a YZ465G new out of the box. Don't get me started as just loved that bike. When i got the YZ490J i wanted my old G back.

When I got into vintage MX the YZ465 was THE bike everyone wanted in the post-vintage Evo class. Now THE bike to have is an early-90’s CR250 for the Revolution class. I’ve only seen a couple of 490’s at the track.