La Pavoni Stradivari channeling on some shots.

A haven dedicated to manual espresso machine aficionados.
User avatar
Kaffee Bitte
Posts: 673
Joined: 17 years ago

#1: Post by Kaffee Bitte »

Last few days I have been getting a channel in the same spot. Initially thought it was just a that I don't purge prior to first shot when partner is over. She is edging towards being a nontaster, and can't tell the difference in the cup. It saves me a little coffee here and there and no harm to her cuppa or taste buds. However it's been doing the same thing on my shot pulled shortly after as well.

Recently rebuilt the Stradivari, new boiler gasket etc. Pulled the group and did lube, clean. No gasket changes as I had done them before the rebuild. Also replaced old beat up shower screen with IMS precision shower screen. These changes were all at least three weeks ago now. Just three or four days of doing this.

Oh. Also both machines newly sleeved with stainless piston sleeve. This has definitely altered some of my usage. Mainly the sound and lever feedback as I lift the lever to let water in. The old plastic sleeves made a good bit more noise and could feel in lever. Now very quiet and much reduced feedback. I have to listen very attentively to hear the water enter, so I have been missing and going fully open. I am sure this is part of my problem, and just need to adjust myself a bit,

Not coffee or grinder issue. Same beans and grind pulling lovely shots on my gen 3 pro.
Lynn G.
LMWDP # 110
____________________

User avatar
drgary
Team HB
Posts: 14284
Joined: 14 years ago

#2: Post by drgary »

Kaffee Bitte wrote:The old plastic sleeves made a good bit more noise and could feel in lever. Now very quiet and much reduced feedback. I have to listen very attentively to hear the water enter, so I have been missing and going fully open. I am sure this is part of my problem, and just need to adjust myself a bit.
Lynn,

It looks like you've probably figured it out. To ease the transition to the stainless steel sleeves I wonder if using a filter paper on top of the coffee cake would ease the channeling?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
baldheadracing
Team HB
Posts: 6170
Joined: 9 years ago

#3: Post by baldheadracing »

My guess is two related things:
- Slowly lifting the lever when uncovering the feed hole in the sleeve. The initial bit of water coming out of the feed hole hits the side of the piston, sending a spurt/stream of water towards the shower screen.
- If the IMS screen rotates to the "wrong" position, then the screen will pass that spurt/stream to the coffee, leading to indentations on the puck.

So one can lift fast for that last little bit, or use a puck screen ...

Here's a short video from Bong showing the effect on a gen2 - which is worse IIRC. The video is a bit disconcerting at first as he fiddles with the camera; skip to 1:05
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

User avatar
Kaffee Bitte (original poster)
Posts: 673
Joined: 17 years ago

#4: Post by Kaffee Bitte (original poster) »

Hmm. So odd that the sleeve would change that so much.
And also odd that it's only happening on one group.

I will try a fast open next round and see if that helps.
Lynn G.
LMWDP # 110
____________________

ojt
Posts: 826
Joined: 6 years ago

#5: Post by ojt »

FWIW I noticed the same thing more pronounced with the IMS screen. Started using paper filters and eventually the mesh after that. From what mr Bong said, on the millennium machines lifting fast doesn't seem to help much. Some say tamping harder does. I just use the mesh or paper and am done with it.

Edit: hmm, or did I switch the sleeve and screen at the same time? Anyway, doesn't change the solution for me
Osku

User avatar
Kaffee Bitte (original poster)
Posts: 673
Joined: 17 years ago

#6: Post by Kaffee Bitte (original poster) »

I do only have the ims screen on the Stradivari. The gen 3 is still a stock shower screen.

I have been using the slow lift at water let for ages as I like that it gets more water in the group. Having done my share of accidental fast lifts over the years, I never really enjoyed those oops shots as much.

I will try some different techniques over the next few days, and see if I can get it improvement.

Edit to add. I am disinclined to start using paper filters, just from a waste standpoint. I will look into getting some puck screens though. Haven't really felt a need with regular cleaning regimen.
Lynn G.
LMWDP # 110
____________________

User avatar
baldheadracing
Team HB
Posts: 6170
Joined: 9 years ago

#7: Post by baldheadracing replying to Kaffee Bitte »

You only have to lift a little bit faster just before the hole in the sleeve is uncovered.

For puck screens, to minimize the impact on available headspace, I use the single-layer one from Coffee Sensor: https://coffeeaddicts.ca/products/puck-screen. I use a puck screen mainly to prevent the mess that can sometimes happen when I use a single-shot basket with lighter roasts. (The puck screen also slows down the build-up of fine grinds above the group gasket o-ring - but I think your machines use gaskets, not o-rings.)
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

User avatar
Kaffee Bitte (original poster)
Posts: 673
Joined: 17 years ago

#8: Post by Kaffee Bitte (original poster) »

baldheadracing wrote:You only have to lift a little bit faster just before the hole in the sleeve is uncovered.
I lock in before lifting as I found the lock in just before water let to be awkward, and I tend to feel awkward enough in life. But lift slowly and hadn't ever had much channeling, aside from the random oops.
Always at point of water let I aim to just open it and then let the lever finish the lift to top with a gentle nudge when it wants too.

You are saying to just finish the lift and let it rip? Or smooth slightly faster lift from open to top with no pause for water fill?
Lynn G.
LMWDP # 110
____________________

User avatar
baldheadracing
Team HB
Posts: 6170
Joined: 9 years ago

#9: Post by baldheadracing replying to Kaffee Bitte »

I also lock in before lifting, and:
- lift up ... slowly, slowly ... keep going slowly until:
- just before the point where water from the boiler will enter the cylinder
- at that point I lift faster from there through to the end of travel (lever all the way up). I'm not "letting it rip" fast, but I am lifting faster.

My wild guess is that the above is what you were naturally doing with the old plastic sleeve, but the new sleeve has the hole in a slightly lower point and/or doesn't give the same feedback into your hand that the plastic sleeve did. I'll suggest leaving the portafilter off to figure out where that "just before" point is.

However, I'm reasonably certain that isn't 100% of the issue. You could also try swapping in the old (stock) screen and see if/how the problem changes.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

User avatar
Kaffee Bitte (original poster)
Posts: 673
Joined: 17 years ago

#10: Post by Kaffee Bitte (original poster) »

Hmm. Honestly the end zone is a bit different than I remember it being. I think the inlet may be a little higher than the plastic sleeve version. The open start is closer to the top than it was.

So just checked and readjusted my lever piston nut. Going to fire it up and see if it was at least partly a misadjusted piston. Luckily a friend is popping by to drink it as I am pretty well dosed at the moment.

Even if that was it, I will experiment with your lever lift variation. Maybe it will be better for a couple of recent SOs I ran through without getting their best.
Lynn G.
LMWDP # 110
____________________