There have been some good deals on z400's on craigslist and I've been throwing around the idea of picking one up.  Just wandering if there are any years I need to stay away from? 

Thanks for the info.  From everything I've heard about them they are good, tuff atv's.

I had a 04' Z400.  Never had a problem with it, but I didn't keep it too long till I parted it out.  Good power for what it is.

Great machines for sure!! Honestly if you get an awesome deal on 03-04 all you would need to do is go to 05+ or 450r or aftermarket of course front shocks and you'll be set. I never had any issues with my frame.
Things to look for specifically when buying. Watch the weep hole on left side(I think) of the cylinder if it is pushing oil out your cam journals cap threads could be stripped and you will need to put an odd ball 7mm heli coil in it (yes it could just be bad gasket but good chance you could have stripped out threads on the cap(s).
Also listen closely to it as the automatic cam chain tensioner applys way to much tension and the cam chain tends to wear out quickly (most convert the stock one into a manual tensioner).
Hope ya pick one up soon! 

They make a great foundation as a starting point for a hybrid!

Z's are the **** man I love mine