Might fix up a YZ400

[nucular]

I have what I believe to be a 1977 YZ400. It is in terrible shape but it is pretty complete so I am considering trying to get it back in riding shape.

The engine is pretty well knackered. The crank bearings feel bad and the big end bearing on the rod is pretty much locked up. The bore and piston are 'fair'. I had considered putting new bearings in but it appears someone jbwelded the crank bolt to the crank so I can only imagine those threads are completely messed up with means doing a little rethreading on the crank too.

I have come across an engine for a 79 (which I believe was different at least internally) for $100 and am debating if it is worth it to buy this engine. My first concern is whether or not it will even fit in the 77 frame. The bikes look similar but I am not sure if the engine mounting locations are the same. My 2nd concern is if this bike is worth dumping $100+ to get running.

any thoughts would be appreciated.

-Kevin

[cowboyona426]

If the motor mounts etc. are the same, for $100 I think it would be a good investment. Clean up the cosmetics on the bike a bit and you should be able to make money on it if you wanted, or you'd have a nice looking old school big bore 2 stroke to play around on!

[OLDMXRACER 393]

"My first concern is whether or not it will even fit in the 77 frame."

I don't think it will, but PM Coopsvintageyz here. If he doesn't know I'm sure he can point you to someone who does.

[bigspeed]

I had a '79 YZ400 year ago. First big bore MX (or any bike really).
What a thing aged 20, it was like nothing else It wasn't till I rode a '86 CR500 years later that I got the same buzz. Not much help to you I know but
'Godamn What a ride' (J.Travolta "Broken Arrow" 1996). I digress, good luck.