Did you ever open up the CVT cover to ensure the the variator is working? In your first post, you said it had a new belt. If it was not installed correctly, the rollers are out of place in the forward section of the CVT (variator) resulting in the transmission being stuck in "high" gear.

Yea but would'nt the motor rev up it just would'nt go fast?

Try to start off the line in third gear with a manual transmission - There is no way the engine has power to spool up. With the CVT it is even worse because the clutch will engage almost immediately so the engine is loaded right off idle.

I know that. I'm thinking on jack stands. I would be in the man cave working on it so I'm just assuming he has it jacked up. It would rev if it was jacked up yes?

Thats why I said in Manco's post that this sugar sand can hold you at 25 wide open. It just cant catch up. The motor will never rev out

Give us a little more info on what is happening when it "doesn't go over 10mph".
If a roller is sideways, you'll get a studder when you first take off like in a manual transmission when you let the clutch out too fast. Once the rpms pick up, a sideways roller isn't as noticable and probably not cause the slow top end. The variator fan not being all the way on will cause that though. If the bolt is cross threaded, it won't push the fan all the way in and the belt will slip on the boss pin .
Another common cause would be if the clutch pads are shot. Check the bell to see if its purple then check the pads.

If it is spitting and sputtering when you try to go fast, I would direct you in another direction such as the CDI or coil or even an air leak in the intake manifold or vacuum lines.

If you have a video camera, that would be a great help. If not, we can still brainstorm what is wrong, just be specific in your descriptions and that will help us steer you in the right direction.
I always say "Check all the stupid and "free stuff" first!
Whatever it is, from the sounds of it, unless a compression test proves that the engine is the culprit, I bet its something you can easily replace once you find the problem. The hammerhead is a great buggy.

Take off your CVT cover and jack up the rear and see whats going on when you press the gas. If you need a "starter course", we have some "How-to" videos that will walk you through some common problems as well as the upgrades we do.

http://www.youtube.com/watch?v=wV_Mw0evQUc

Good luck!

It doesn't pop. Now it wont start. But when I got it running last night it idles ok and when I give it gas it sounds fine but it seems like it isn't getting much power. Like it is running half speed or something. Hard to explain.

Ok, got it started. Sputtered at first when I gave it gas for the first few minutes. After that, it idled fine, never stalled, but it just doesn't have any power. Still goes about 10 miles an hour full throttle.

If it's jacked up does it rev out?

I know its hard to describe a "feeling or sound"
Let me try....
I think this was asked before but does it rev up high and only goes 10 mph? (Kind of like peddling a 20 speed bike in 1st gear. Your peddling your butt off but not going anywhere fast!), then the Belt or clutch is probably slipping (CVT issue)

If it feels more like a big 400lb guy sitting in the cargo rack or sounds like a lawnmower being run in grass that too tall for it, it could be an air leak or carb/fuel flow issue.

On a more simpler note, a slack throttle cable would make you smack your forehead!
Just hang in there, we'll get it!

Being I know absolutely nothing about engines and what not, I will video me starting it and driving it. I will post it as soon as I can.

Thanks everyone for all the help thus far. I really appreciate it!