The small part behind the “click” of the KB90
Anyone who works at a KB90 knows the sound: the portafilter goes straight in, a short, solid click, and it’s seated. That click comes from the clicker arm of the locking mechanism – and this arm is fastened with exactly this screw. If the click becomes soft or spongy, or disappears altogether, it’s worth taking a look at the mechanism behind it.
This is the original part from La Marzocco, part number F.3.100. It isn’t an ordinary screw but a position that belongs to the kinematics of the locking arm – which is why it also costs considerably more than a standard part of the same size.
When it’s due
The portafilter no longer engages cleanly or doesn’t hold reliably. The arm has noticeable play. During servicing, wear shows on the screw shank the arm works against. Or the screw was damaged while dismantling the locking mechanism – it sits deep in the group and is delicate to remove.
At a glance
| Type |
Screw for the clicker arm |
| Location |
Brew group locking mechanism, on the clicker arm |
| Fits |
La Marzocco KB90 |
| Scope of delivery |
One screw, without arm |
| Part number |
F.3.100 |
| Version |
Original part; the manufacturer’s specification does not state thread, length or material |
| Installation |
Installation by a qualified technician recommended |
| Brand |
La Marzocco |
Important for installation
The clicker arm is part of the locking mechanism that holds the portafilter under full brewing pressure during extraction. This is no place for trial and error. Beforehand, the machine is disconnected from the mains, depressurised and cooled down, and after reassembly the locking mechanism is checked for a secure hold. We deliberately don’t give step-by-step instructions here – this work belongs in professional hands.
Who it’s for
For service companies that overhaul KB90 locking mechanisms, and for businesses with their own technician that run a machine in continuous use. For home users without service documentation, this isn’t the right part – calling a service technician is the quicker route.
Related parts
The same assembly includes the Locking hook kit Straight in, the Portafilter holder kit 2.0, the brass bushing for the locking mechanism and the matching M4 × 12 screw. All parts for the machine can be found under La Marzocco KB90 spare parts.
Workshop tip from Bern and Zurich
This is our routine, not a manufacturer’s specification: when a KB90 starts accepting the portafilter “softly”, we first check the locking mechanism by hand while the machine is cold – no coffee, no pressure. You hear and feel the difference between clean engagement and play right away. Only then do we open it up. Meanwhile, we’ve got Very Nutty running, more under Coffee beans.
No returns
Original spare parts are excluded from exchange and return. They are procured specifically for each order and cannot be resold after installation or a test fit on the machine. So before ordering, please check the model, year of manufacture and serial number of your machine – or drop us a short message and we’ll clarify the fit together. Your rights in the case of defective goods remain unaffected.
Frequently asked questions
Why is there no picture for this item?
Because no product image is available for this position. We list the part anyway rather than leaving it out – and would rather describe openly what we know and what we don’t. If you need a picture for identification, write to us and we’ll check in our workshop.
Is the clicker arm included?
No. The screw is supplied. The arm is a separate position.
What thread size does it have?
We have no verified information on this, and we don’t guess. The part number F.3.100 in your service documentation is what counts.
Can I replace it myself?
The locking mechanism holds the portafilter under full brewing pressure. We recommend installation by a qualified technician and deliberately don’t provide installation instructions here.
Can I pick up the part at your showroom?
Yes. We have two locations: Bern at Gerberngasse 44 and Zurich at Hagenholzstrasse 50b. Drop us a short message and we’ll have it ready for you.
Questions about fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
