i was thinking about 2005 z400 or honda foreman S i do trail riding little mud water and some rough trails
please help

 

My moto is "never ride a utility anywhere you can ride a sport bike". That said, you need to decide if your trail conditions really require a big heavy 4X4 beast (that Foreman is 200+ lbs. heavier than the Z!). You don't say what part of the country you are in, but if you are in serious mud, a lot of water crossings, and really rough stuff, you may be stuck with the ute. Plus, the 4X4 will serve you better when there is snow on the ground.

You said "rough trails". The Z has a rather revvy powerband, and doesn't like to be lugged down. It is better suited for more open trails. So, riding along slowly on a technical trail, isn't the Z's cup of tea! If you want to ride tight, more technical trails on a sport machine, the Honda 400EX is the better choice. You can stick it in first gear, and just idle along through the rough stuff. With full chassis and swingarm skids, you might get by???

 

get the z unless you absolutely need the 4x4