Alright, here goes.
As I said, I'm pretty sure I've nailed it using just parts from the TK. I'll be leaving a bottle hooked up for a week to see if it loses pressure before I'm sure.
The only extra part involved is an extra white washer from another tap king lid. I'm sure there are many substitutes that could be found.
Pictures speak a thousand words. Let's start there.
Start off by disassembling your lid like so.
Take the yellow plastic part and shave a 45 degree chamfer on the inside top edge. This turns the two plastic parts into a compression fitting when screwed together.
You know you've shaved off enough when the rubber seal fits snugly while on the neck of the 8g bottle.
From here you will need to push the bottle through the white plastic collar. Push the o ring over the bottle. Add 2x the little white washers that came out of the yellow plastic part. Don't forget to add the pin in the usual spot before assembly.
Once you have that lot in hand you can carefully screw the white collar and yellow sleeve together. It will look like this when done. Don't go too hard on the pliers as a good snug fit is enough. The two parts didn't fit against each other tightly when I did mine and it still works just fine.
Throw in 7x 5c coins and drop the cartridge assembly in. These work but they are leaving stress marks on the cartridge holder along the leading edge. Cutting down an old bottle as an extension would be a better long term solution.
Reassemble the lid. If you don't understand each part, take the time to work out what they all do. If you have any problems it will help.
From here you can just throw the lid on a bottle and use as you need.
The only downside to this method is the use of the extra white washer from another TK lid. An easy problem to solve if you have half a brain.
The original system relies on a double seal on the head of the co2 cartridge. Copy that and you'll be fine. Both are very important.
I did have two other modifications that would work, but this one is the most simple. They both involved machining the yellow plastic part to fit suitable o rings.
They work fairly well so don't stop exploring that avenue.
Someone with a mini lathe could easily manufacture a work around.
HTH.
Ross.
