Ok, update time.
I received my 4 gicleurs a week or so ago but have been busy with cattle at the Royal Melbourne show.
The first one I drilled out from 0.6mm to 1.5mm as this was the drill which fitted snugly into the original.
Result : moving the paddle from 2 o’clock to 6 o’clock made almost no difference, the FCD only seemed to take effect from 8 o’clock to 10 o’clock and could not stop the flow completely.
It turns out that the pin is either tapered or, more likely stepped with the free end being 1.3mm and the base end being 1.4mm.
I tried drilling with a 1.4mm drill bit and then machining the first section with a 1.5 mm diamond bit but slipped just a bit far.
Result : better than #1, the FCD kicks in around 6 o’clock but still does not completely stop the flow.
This means that, while I can stop the pre-infusion at 2 bar, it keeps creeping up to about 5 bar in the 20 secs I normally use.
I have chamfered the inner edge of one of my gicleurs to try and take account of the broader base of the pin with no change to the results.
I haven’t made any modifications to the pin.
Next I am thinking about using some valve grinding paste between the flat surfaces of the pin and gicleur in case they aren’t meeting flush once installed.
If anyone has a source for the original gicleur I would be interested.
