I wanted to add how can you tell if the motor locked up is it possible ? When it starts with clicking noise?

Yea I am no expert either but when you turn your key on does your neutral light come on?

Check the obvious things first. Main Fuse/Ignition Fuse, Spark Plug, and fuel.

The neutral light works, I did check the fuse under the seat it is good

Pull the sparkplug and see if it turns over.

Ok I checked everything to the starter it all looks good. Ok where the starer is their was a round plate that had three bolts I took that off and and this gear deal came out I tried the starer and it was working fine but the gear part the the starter turns was realy had to move I dont know where to go from here? Whats next to check or does it mean something?

Can you start it with the recoil start?

The z400 is known to have some starter issues. Since they were designed for MX racing at the time, the starter is very light duty and cannot take abuse. I've heard many of them going south prematurely.

The gear you pulled out is the starter clutch I believe. And it can lock up if one of those gears is sheared or even cracked. I have pulled mine out to inspect it a couple times during oil changes to check for wear because I know they have had problems.

The good news, is that you can go on Ebay and probably find a few z400 starters in real nice condition. Or call East Coast ATV and ask them if they have one. They probably do.

Make sure you replace that o-ring gasket, you don't want to re-use it.

There is none on a z400..... In fact very few if any sport ATVs have a recoil backup anymore...... The last one I remember with a recoil backup was the old Warrior, which Yamaha stopped putting in sometime in the early 1990s.