SOTP Vintage Series
Main Motorcycle: The one between my legs
Join Date: Feb 2009
Location: Upstate NY
Other Motorcycle: A few
Extra Motorcycle: Yes
Personally, I'm not a big fan of retapping holes in aluminum unless there is no other choice. Here is what I do.
1. Clean the tapped holes with carb cleaner or brake clean. Put the little straw nozzle in the hole and blast it clean. Then blow it out with compressed air.
2. Visually inspect the holes. If some are still dirty, go at it again.
3. Take a screw that has good threads but will not be reused, and cut an axial slot with a hacksaw blade down the side. DO NOT split the screw. Clean off the burrs.
4. Run the screw into the hole with your fingers. The slot will provide a place for crud to go rather than being swaged deeper into the thread the same way the relief slots on a tap provide a place for the metal chips to go.
5. As you are running the screw in, if you hit a hard spot, give the screw a light tap with a small ball peen hammer. This will move any displaced thread material back into place. The screw should continue to turn by hand after the tap. You may be wise to back the screw out after going half way and blowing any crud out of the slot before running it all the way to the bottom.
This procedure should maintain as much original thread material as possible and still clean up and reform your threads for the reassembly process.
If you buy a tapping fluid to use with your screw, or if you have to retap a hole, be aware that some tapping fluids will react with aluminum and destroy the thread. I'm going back into my memory banks here, but I believe Tap-Free is one that works great on stainless, but will destroy aluminum.