Bicycle Mechanics - Headset ?

Are there different length headsets available? I see you can get headset spacers. How do they work? Will they raise the handlebar?
The reason for my question is I need to raise the handlebars on my Kona Dawg as much as possible.
I'm planning on trying a 130mm/25 degree stem and a 2" riser bar.
Thanks

Short of buying a new fork with a longer steerer column you have two choices.

The first is a stem with more rise angle. If you choose to go this route, select the length carefully because, besides raising the handlebar, it's also moving it closer to the saddle.

The second is a device similar to the Zoom HeadsUp. It clamps onto your fork's steerer in place of your stem and allows you to reinstall your existing stem 23mm (almost an inch) higher.

Thanks Grouch, I had never heard of of those.
Are there any significant problems using these on a mountain bike?
Here are links for a 75mm one and another brand that is up to 3 1/2" that comes in black. Do you think they would work? My headset is 1 1/8" threadless.

http://store.airbomb.com/Itemdesc.asp?IC=SM2787&link=qbike

http://www.nashbar.com/profile.cfm?category=119&subcategory=1186&brand=&sku=4264&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20ATB%20Stems



The second is a device similar to the Zoom HeadsUp. It clamps onto your fork's steerer in place of your stem and allows you to reinstall your existing stem 23mm (almost an inch) higher.

I honestly don't know. My total experience was seeing one once on a cyclocross bike but I didn't ride the bike and didn't even talk to the owner. It wasn't as kludgy looking as I would have expected so that's good news.

Your headset doesn't really matter. It just holds your fork in place in the frame of the bike. It has nothing to do with how high your handlebars are. What matters is how long your fork steering tube is. If this is not long enough for you, you either get an extension for the steering tube, a la the Zoom Headsup or you get yourself a stem with a greater rise.