I have 12 horse power briggs ohv that was someone tried work on. They took values loose and carb off, I have put back together and set values on 4, the motor will fire right up but no power. Any help would be appreciated.

Hi,
Sounds as if the valves are set correctly at 0.004" from your description. The YouTube video on this is:
Lawn Mower Repair Valve Adjustment - YouTube (http://www.youtube.com/watch?v=NjzX-PUjKmo)
And it will show how to check what I am going to tell you. Remove the plug so that the engine turns over easily, remove the valve cover and rotate the engine while observing the rocker arms that open the valves. They should move the same amount. If not then you probably have one of the bad camshafts that had the exhaust lobe not hardened. You can also see how to check your friend's work.
Peace,
Clarke