So my z400 wasn't starting well (you'd have to give it a lot of gas), spark plug was good even tried a different one just in case. So my husband decided it must be a dirty carb. He took it apart and when taking off the diaphram cover the spring inside shot out and we couldn't find it. My husband happens to have a broke down '69 beetle and decided to take the same spring off it's carb it appeared to be a perfect fit. He cleaned it all and put it all back together and tried to start it but nothing, the engine turns over but it won't fire up. He was examining the tps and thought the white plastic dial in the middle seemed too loose, like it shouldn't be that loose. Don't know if this has anything to do with anything. As far as he can tell everything is in it's place and where it should go. Any ideas??

 

Could be that you didn't plug the vacuum line back in to the carb, and there is also the possibility that if it was hard starting before your intake valves could need adjustment.
I don't think the tps would prevent it from starting. I have an '05 carb (with tps) on my wife's quad and it is an '04 so it can't even be plugged in.

Try bump starting it.

 

Yeah, looks like it's the valves. Anyone know how to adjust them?? Is it the same as for a car??

 

its nothing like a car

 

Here's an overview. Do a search for a downloadable service manual if you don't already have one. You'll need that as well. It's not hard, you just need to understand what you're getting into.
Checking Valve Lash/changing Shims - Suzuki Z400 Forum : Z400 Forums

 

My husband wasn't all too sure how to adjust the valves so he took it to a mechanic. Turns out they were in pretty bad shape, but all better now. I started her up and she sounds better than when I first got it a year ago. I borrowed my husband's 450 Honda this weekend and missed my Suzi SO much. I can't wait to take her out again this coming weekend.