I could've just deleted the previous post, but anyone who has spent any time with me at all will know that sometimes I just get it hopelessly wrong. Part of my penance is to admit this at every opportunity.
This time, it was the tyre valve stem. The valve is spring-loaded and will not open with just a few KPa of CO2 pushing against it, which is why inflators have a little pushing dingus inside them: to open the valve (duh!). So, I've shown my hand and posted the Party Keg Update too soon - before testing the device in question.
I found this out while trying to carbonate a small batch of cider. The cider is very good and suggests an appley good future.
