One big problem i see from people on these forums is they have a problem or something, they then go and change several items in the one hit attempting to fix it and end up wondering why their bike won't go like it used to.
The key to fixing a bike (or anything else for that matter) is to eliminate problems one at a time.
In this case, you bent a valve so you replaced the head. GOOD!! Once you've changed the head, put the thing back together and make sure it runs with everything else as it was. Its only a 10 minute job to put a new carby on so make sure the bike runs first, then when its going properly, THEN change the carbie. You also changed the manifold, if it is not set up for that carbie then perhaps your engine tune will not be correct. But the moral is, only alter one thing at a time and eliminate problems. Same goes if your making mods, change one thing at a time and make sure it works properly after every alteration!
As for your problem, its a bit vague to just say your bike doesn't have any power. Does it sound like it did before? Does it have any rattles? Does it backfire? Is it blowing smoke? Have you run the engine in after changing the head? Is the head sealing properly? Did you use a new head gasket? Is one of the new valves sticking?
You can see the predicament. Give your beast another run and listen/look very carefully at what has changed since doing your work. When you can nail a few things that are different, jump on and give us a bit of a more detailed description and i can bet that your problem will be solved pretty quick.
Good luck man, hope she gets back on the gas soon.
Always start looking for problems where you have been playing first. Why would it be the carby or manifold if it was ok before your fiddle?