Rebuilding the Riviera group is a straightforward procedure which involves removing the spring loaded piston, refreshing the seals, and reinstalling the piston. The most common piston retains 3 seals on the piston. The seals are called U cups and they have a cupped side and a flat side. When you take apart your group take note of the arrangement of the seals on the piston and install the new ones in the same manner. the example which follows is done on the type of Riviera which has two seals and now 3....the method is the same for both.
You will need the follow tools at minimum
- 10 mm wrench or crescent
- blunt probe for seal installation
- hooked tool (paint can opener) for shower screen removal
- wood sticks for pin clip removal
- clamp or home built jig for spring compression
- short dowel or pipe for use with clamp
- Dow 11 or other suitable cylinder lubricant
Remove the group from the machine using 10mm wrench.
Remove dispersion screen with hook tool by catching the rim of the scrren with the hook and pulling straight down....do not pry....pull straight down and it will pop off.
Remove the group feed tube using 10mm wrench
Place clamp (I use a big wood clamp as it is what I have but I have also used an Irwin type quick clamp and a C clamp.....the latter two have a tendency to slip off) in such a manner that one jaw is resting on the top housing from the back, making sure that there is enough room for the rod to travel upward and the other jaw is over the piston face. Use the short dowel or pipe as a tool to reach in to the group. Double and triple check the clamp placement to make sure it does not slip off either end.
Tighten the clamp a slight bit until the clips and pins can be removed from the lever yoke...it does not take much movement to release the force against the pins. Remove the pins.
Release the clamp so that the spring is slack.....about 1/2 inch of travel is all it takes.
The piston is now out....remove the piston and spring. Remove the old seals and clean the piston and seal grooves as well as the cylinder. Use whatever cleaners are needed to remove old coffee and scale. DO NOT SOAK the entire group in descaler....this could remove the chrome finish from the outside of the group!!! If you need to remove scale from the cylinder do so manually with pick or scotch brite pad.
Install new seals on the piston using the blunt probe to make sure they fit well and are even and seated all around in the piston grooves.
Installing the piston is a bit more complicated than removing it....
Lubricate the cylinder and piston seals with Dow 111.
Insert the piston with spring into the cylinder making sure you align the lever pin hole in approximately the proper orientation. The spring will not engage until about 1/2 inch from the end of the cylinder but the first seal will enter before spring engages. Hold the group in one hand with your thumb on the piston face and the edge of the first seal against the cylinder edge. Apply pressure with your thumb while working the edge of the seal into the cylinder by use of the blunt probe. You are essentially using the probe as a shoehorn to make sure all of the edges of the seal fully enter the cylinder without tearing or gouging the seal.
Keep squeezing the piston with your thumb until the seal is all tucked in and POP it will go in to the cylinder.
The second seal is a bit more difficult because at some point the clamp will have to be applied to begin compressing the spring.
Set up the clamp as before with your short pipe against the piston face and the other end of the clamp on the top toward the back side of the group.....make sure you have enough room to allow the piston rod to pass the edge of the clamp and that the lever can be installed when the time comes.
Begin tightening the clamp until the second seal begins to enter the cylinder....this is a bit trickier as it is the U side of the cup which is entering. Use your probe to make sure that the edge of the cup is entering all around....use good light and keep checking and shoehorning until you are certain it is entering properly.....loosen the clamp if you have to and tighten little by little all the while monitoring the seal progress and tucking in the edge with the probe. Once you see that all of the edges of the seal are safely inside of the cylinder, continue tightening the clamp.
The third seal will go in much easier, but again continue to tighten the clamp slowly and monitor the progress of the seal as it enters the cylinder. Failure to properly gentle the seal into the cylinder will destroy the seal!!!!!!
With the piston all the way in, apply the lever yoke....if the pins do not slide through easily check the alignment of the piston rod hole. Insert the piston rod pin and then the bushing and fulcrum pin. Install the clips.
Remove the clamp.
Install the dispersion screen by snapping it on using even pressure with your thumbs.
If you are replacing the portafilter gasket, do this before installing the dispersion screen.
Cautions and thoughts
The biggest issue here is the safe entrance of the piston seals into the cylinder. Take your time and make sure they are all tucked in before tightening the clamp....use good light and check and double check during this part of the procedure. Do not get excited and forget the spring!!! Use plenty of lube but you may want to use a nitrile glove to apply the lubericant.....if you have a coating on your hands and tools and clamp, things can get pretty slippery real fast. The clamp is important and can slip off.....this is a source more of aggravation than danger, as the spring is near its at rest state while installed.
As always, keep in mind that there are many ways to do the same job and this is but a guide....you may have a better method or a better clamp or seal chaser....all's the better!!!!!
Hope this helps.
Barb and Doug