Here are some photos of the Bianca E61 control valve assembly. I was interested to check the design detail and its condition after 557 cycles on the shot counter.
I left descaling until after this exercise. Lelit recommend descale at monthly intervals and it looks that this will be the correct thing to do. This is two months from first use. You'll see that there's some moderate loose scale on the valve gland seal and the mushroom. I live in a moderate water hardness area, nominally, but Yorkshire Water Authority network their water around the county, so hardness and mineral content can vary. I've maintained the refill counter and used a new Lelit filter as required.
Checking torque with a traceable calibrated wrench, before disassembly, I found the torque settings used to be low, at 6-8 Nm for the metering valve chamber sleeve nut and 8-10 Nm for the Mushroom sleeve nut. These values make sense for the moulded polymer washers used, which are of high quality. stepped as required. I rebuilt the assembly to these torque values with a smear of HT silicone grease. The assembly photos are after reassembly and with the machine at operating temperature. No evidence of leaks.
If rebuilding your own Bianca, I'd recommend use of 12 point sockets (22mm and 36mm sockets needed) and an accurate torque wrench. This will avoid damage to the surface chrome or distortion of sealing washers or the valve seating and alignment. The paddle clamp screw is a 2mm hex socket.
Fit and finish of parts are good to high standard, with good machining attention paid to bore and thread form to control the centring of the metering valve and jet - users will notice the smooth operation of the paddle and its metering is very repeatable when measured. An exception is the mushroom which is already showing signs of surface corrosion degradation.
The metering needle is 4.8 mm in operational length and tapers from 1.45mm at the shoulder to 1.28mm diameter at the tip. Measured at 5 points, this is a constant taper grind. The jet measures around 1.4mm diameter, but my measurement technique of the jet bore with a plug gauge, is not very accurate.This is a finely made assembly and delivers accurate repeatable control. Scaling or contamination here will degrade metering performance so maintaining group cleanliness and monthly backflushing are going to be required for keen users.
I'd advise measuring outlet water flow at operating temperature, before removing the paddle and opening the valve assembly. I had a graph of flow from the group at 6 points of paddle position, posted elsewhere on H-B,but four measurement points will be enough. You'll need this data to return your paddle to its previous flow set points. One spline change can make a 5-10% difference in flow rate.