Bent piston -- can it be fixed? - Page 2

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IamOiman
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#11: Post by IamOiman »

beer&mathematics wrote:Ryan, after the initial tears I am indeed very happy to have a new piston available :wink: Also, LaMacchinaDelCaffe is awesome! Used them last year to get a bunch of parts when I rebuilt my Export (remember it was in a box in pieces when I moved from NYC to CA). What I really like about them is that you pay 25 euro for shipping but they will refund you a certain amount after they process your order. This time I got a 18 euro refund so shipping was only 7 euros-crazy!

About the cylinder, it does look a little wonky by eye but not too bad. I'll just have to wait and see if it works after the new piston arrives.
Yea they are really good. The refund is a partial (if not full) VAT payback since you are not in the EU if you are curious about that.
-Ryan
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JohnB.
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#12: Post by JohnB. »

beer&mathematics wrote:Thanks Jason and Tim-I learned a new technique "hone a cylinder". Will read up on this a bit before I try it and thanks Tim for the image so I know what to look for.
Is works well depending on how much material you need to remove. I used a brake cylinder hone to clean up the bore of my Cremina 67 when I rebuilt it.
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IamOiman
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#13: Post by IamOiman »

Sometimes there is very light wear from use on the bore too, this example from my Urania after sanding it to 2000 grit (starting at 1500). This particular wear is only visible from certain angles and I could almost not feel it without considerable effort. From the many Zodiac groups I've fixed up I think as long as there is no burr formed and the wear is very small you should be fine, do you have a pic of your bore you can show us if possible?


Basically make sure it does not look like this :D
-Ryan
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beer&mathematics (original poster)
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#14: Post by beer&mathematics (original poster) »

You win some, lose some.

Okay, so I found some time this week to work on my Sama. First, the fun stuff. I played around with vinyl wrap and finally changed the color on my Sama from red to yellow.





Not perfect, but pretty decent. It is a huge upgrade from the original paint that had two giant scratches on the side (bought it like that). I wanted to get it powder coated but the only place near me that would do it said they start at $175 :( I thought it would be in the 60-100 range but 175 is steep, and that was without the powder. Anyways, I already had the vinyl wrap on hand since I bought some in the summer.

Next, I rebuilt the group. If you recall, I broke the piston when trying to instal it a few weeks ago. LaMacchinaDelCaffe to the rescue: I bought a new piston and it came super fast. In 3 days. How is that even possible? Anyways, I thanks the heavens since the piston can with new seals already installed. I truly hate installing the 45mm Export/Lusso seals :evil: so that was a big relief.

Sorry I forgot to take a picture of the inside of the cylinder. It looked like it was in good shape visually. I wasn't distorted to my eyes. It also was super smooth inside. I ran my fingers and didn't find any rough spots so I cleaned it up in there and added a thin layer of dow111 and installed the piston. I managed to install the piston without any hiccups this time!

I do have the Ponte Vecchio piston removal tool, which comes with a small cylinder to help maneuver the middle upwards seal. All looked ok so I re-assembled the machine and ran a quick test. Yes! Lever action is sssmmooooooooootthhhh!

All looking good so I got a basket ready and pulled a shot. The coffee I'm using is dialed in to my La Spaziale Vivaldi with a Niche Zero grinder and I kept the same settings for the test shot (usually this would choke the machine).

Here's the strange part. The lever doesn't catch at all. It just comes straight up with no resistance (but still so smooth lol). I pulled it about 15 times to get about 15 grams of coffee with no resistance. What the heck! I haven't experienced this before. Any ideas on what this could be?
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miab
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#15: Post by miab »

If that's a thermosiphon group be careful you have enough water in there. you might see water nearing the bottom of the sight glass and think your good but if too low, you are pulling steam into group on pulling lever along with little water. lever will go back up with no resistance from the puck.

Sorry , I think I saw the dipper tube in one of your photos.

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beer&mathematics (original poster)
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#16: Post by beer&mathematics (original poster) »

Hi Joseph, it is indeed a dipper tube. I always fill my machine so the sight glass is full with water (with a few centimeters of space left clear).

I did put some Teflon tape when I connected the dipper tube (am I using the correct term?) to the group so it would be straight down. Without it, it would insert at almost a 45 degree angle which I didn't want so that's why I put the plumbers tape.

I am wondering if maybe the tape is the problem and causing a blockage. I did this tape trick a year ago and didn't have any problems. I'm stumped!
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mikel
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#17: Post by mikel »

You probably already considered this, but how much Dow 111 did you put in the cylinder?
I try and keep it to a light coating on the seals...

miab
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#18: Post by miab »

If the dipper tube cracked at the bend or somehow when you screwed it in to the group there is a leak , it will suck steam in on lever pull. A little water will still come through and that is why you pulled so many times to get 15g. Your vacuum is somehow compromised. That would be my first look.

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peacecup
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#19: Post by peacecup »

With the pf removed, does water spray from the group when you pull the lever down (when up to temperature)? If so, the dipper is not at fault.

I sounds like: a) the bottom seal somehow get damaged when re-inserting the piston, b) too much lube, or c) the new piston is slightly narrower. In the later case you will need to find some slightly thicker seals or add a spacer under the seal to create enough pressure.
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miab
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#20: Post by miab »

Water will still come out with portafilter removed and lever cocked. Although less than if everything is working properly. When the puck in a portafilter is mounted even less water will flow if there is a leak in dipper tube above water level. Looking at your photo of the dipper tube, the underside of the bend looks brazed/soldered. I would look there first. Might have cracked when reinstalling. I doubt just the bottom seal doesn't fit the bore. If both seals didn't fit then water would have gotten above top seal and water would have come out the top. If just bottom seal is decayed your water in tank will have coffee in it. Dump it out into white bucket and check.