LPowners.org Adjusting piston throw

by Bruce Colglazier Pappas

Goal: to have the piston at its lowest point - almost touching the shower screen, giving it the maximum throw.

Purpose: when your piston has the maximum throw, you maximize the amount of liquid you get out of each pull. Also, this may help purge excess air in grouphead.

You don't need to remove the shower screen and gasket to adjust the piston throw.

  1. Remove the cap nut (on top).
  2. Back off the retaining nut, almost to the top of the threaded pin.
  3. Insert your portafilter (with or without the basket), so that the shower screen is held in place.
  4. Lower the lever gently until it can go no further.
  5. Tighten the retaining nut all the way down.
  6. Pull up on the lever, so that you can tighten the retaining nut one more half turn. This extra half turn keeps the piston off the shower screen, so the piston won’t push it out.
  7. Lower the lever again.
  8. Reinsert the cap nut and hand tighten.
  9. While pushing down on the lever (thus holding the retaining nut in place), use a 14mm wrench (I prefer a socket or closed box wrench) to capture the cap nut against the retaining nut, so neither move. Do not overtighten; the retaining nut should not move during this process.

If you do have the shower screen and gasket off, you can just look (or feel) for the piston to be even with the bottom of the sleeve.

You’re done! Enjoy the fruits of your labor now by extracting as much liquid as you can out of the grouphead.

Created 08-MAY-2017 | updated 05-FEB-2023 | BCP