I'm in the process of trying my first flashlight mod!!!
It's an Ultrafire K41. This is a cheap low-quality 1xAA zoomable.
One of the big issues with the light was that the lens was too far from the emitter in flood mode. As a result the flood mode produced an extremely narrow cone unusable illuminating things up close. This pretty much negated the point of of a flood-to-throw zoomable light. After examining the light closely, I determined that filing down the part of the body that stops the bezel's retraction towards the tail when switching to flood mode would allow the bezel to slide further back and the lens to get closer to the emitter.
I spent an hour with a file and successfully filed this down allowing the bezel to retract an additional 3-4 mm. Upon further examination, I determined that the LED could get even closer to the lens. Rather than doing extra filing, I instead used a small paperclip and bent it into a ring. I put this at the top of the pill to prevent the pill from screwing down all the way. I then used some black paint and a permanent ink pen to try to hide the chipped areas of anodizing where my file had slipped.
The result is actually pretty decent. In flood mode the light is smaller than it was originally, making it even better for pocket carry. Also, the additional range of motion of the sliding mechanism made the flood more much more usable. It's now about the same width as that of my stock Sipik 68.
Another thing I did was to change out the switch boot for a black one from Shining Beam. The switch was sticking when I did this, but that was solved by replacing the plastic washer below the switch booth with a metal one. However, one disadvantage with this is that the original, the switch boot is rounded and sticks out well beyond the metal flanges at the bottom of the light so it cannot tailstand. To make it tailstand I need to find a flat switch boot.
Does anyone know a supplier who sells 14 mm switch boots with flat tops? Preferably in black color.
I'm also thinking of trying to disassemble the pill to switch out the emitter and driver. As-is, it's noticeably dimmer than my Sipik 68. I'd like to put something stronger in it for more lumens. Also, the original emitter was shoddily installed. Instead of facing straight at the lens, it's tilted at an angle.
Anyone know the best way to disassemble the pill? It seems to be glued together. Maybe freezing / boiling cycles to weaken the glue, then try to pry it out with a pliers or knife?