I think I saw a brief mention of how to do this in one of the past posts. I was bored last week so I scanned through all 300+ pages of great posts so far. However, I don't remember seeing a detailed post on this. Since I was doing this mod today in prep for ape hangers I thought I'd take some pics and post a how to.
As most if not all of you already know the standard 1/2" bolt used for HD risers is a slight bit too big for our bikes. That stinks because there are so many cool HD risers, many of them costing a fraction of what metric risers cost. For instance, the ones I used for this mod, although they have been laying around in my garage for at least 2 years, were gotten off of ebay along with a slightly used drag bar for only $35 bucks total. I will use HD risers for the apes but not necessarily these. I'll be ready for them though with this mod.
These mod pics start from the point where the bars and risers have been removed. An allen head wrench for the riser clamps and a 14mm wrench for the nuts holding the risers, located underneath the top triple clamp, will get you to this point. Be careful removing the chrome plastic caps (if you got 'em) that decorate the riser clamp allen heads. Protect your tank, headlight and forks with a towel or other soft material when doing any bar or riser removal.
What you end up with is this:
The two holes where the stock riser bolts go through have what is essentially made up of metal cup on top and bottom, encapsulating rubber that dampens vibration. Twist one of the top metal cups with your fingers and it will pop out. You'll discover a metal sleeve running through the middle.
That metal sleeve will pop right out.
You can see on the next pic below that the 1/2" HD riser bolt will fit through the rubber with the sleeve removed. However, the holes in the metal caps, both top and bottom, are a little bit too small.
You need to make these holes bigger. Get a drill and a 1/2" drill bit made for drilling metal to open these holes enough for the HD riser bolts to fit through. You can drill these on your workbench, but I found that setting them back the triple clamp to drill them helped me hold them and kept them from spinning. Again, be sure to have your tank covered in case you slip up somehow.
After drilling the two top ones, I pulled them out and put the two bottom ones in the top holes, again to help hold them, and drilled them.
At this point the modding was done. I put the top and bottom metal cups back in place (remember that the chrome ones go on top) and installed the HD risers with 1/2" bolts.
If you ever want to put the stock risers back on, just put the metal sleeves back in the rubber mounts and you'll be set.