So if the problem it's in the motor shaft, replacing the burrs do not solve the problem, right?

oton wrote:So if the problem it's in the motor shaft, replacing the burrs do not solve the problem, right?

Correct. If your car has poor alignment of the wheel axle, that cannot be fixed by replacing the tires.

If the problem is in the motor shaft then you need to replace the motor shaft, and if you need to replace a motor shaft then most often that means getting a new motor (or more likely a new grinder)

another_jim wrote:AFAIK, a lot of grinders have adjustable motor mounts, so the shaft can be trued after it goes out of alignment.

If the shaft is still straight, then how did it go out of alignment?

I suppose if these adjustable motor mounts had moved or come loose then the assembly could be re-aligned (and I believe it would require turning with an indicator)

But if the shaft is bent then adjustable motor mounts won't help any more than new tires.

I did the test. I painted the top burr with Nutella (a very fine layer with a brush) and I screwed it to zero point.

Lower burr:

But what does the top burr look like? As long as the top burr has an equal smudge around it, you are good. If one side is smudged and the other solid, you could still have a problem.

Well, I apologize for not following up on this. While I haven't posted anything lately, I've certainly been trying all manner of things to get my espresso back to normal. After a number of failures, I finally figured out what it is: water pressure. It took a lot longer to figure out than it should have, primarily because my brew pressure gauge is not connected right now (I broke the brazing of the end fitting of the gauge pipe a couple months ago and have been woefully lazy in getting it replaced). Apparently my inlet pressure regulator was wide open, which the last time that I checked was about 40-45 psi. The pump bypass was set to ~9 bars on the machine gauge for that inlet pressure. I happened to look at the pressure regulator gauge Sunday afternoon, and... it was just over 60psi during brewing.

So I dialed it down to where it was supposed to be and pulled a shot. Same parameters as before the adjustment, pour time went from maybe 28-30s to 45s. Seemed like quite a jump. I dialed the grinder in again, and magic happened. Not spectacular shots, but that unpalatable off acidity/woodiness was gone on all the shots I pulled. I could breathe again.

I was really skeptical of the "fix," particularly because I still don't know what the actual pump pressure is for 60 psi. But After a few more days, crazy as it seems, the pressure reduction has fixed my crappy coffee problem. It doesn't make a lot of sense to me (again, the perceived degree of the issue), but for now I am leaving the pump bypass alone so that when I get the gauge back together (just ordered the parts to do so) I can check the output pressure readout at this setting, when I raise the inlet pressure back to 60 psi. That may shed light on this, or befuddle me even more.

HB Espresso Guide wrote:Proper espresso extraction occurs at 8 to 10 bar of pressure. The higher pressures in this range intensify the flavors.

I asked Jim Schulman if he would consider this the final word on high brew pressure. For me, it seems to have intensified flavors and imparted some really off flavors. My pours were not looking as good as they usually do when this problem came up and I suspected the grinder. Now the setup is back to the original consistency, really great-looking pours all the time, and back to good shots on the palate.

I guess it goes without saying that high brew pressure also reduces the forgiveness factor, as I've seen, and that would contribute to how bad my shots have been; however, even the ones that poured 'just right' were funky, so I don't think that's really the whole story.

Commenting on the article I quoted above, Jim said:

another_jim wrote:I wrote that based on limited experience. My guess is that Italian "custom" here is meaningful, but as usual, not part of anyone's conversation, not even theirs ....

.... when a new machine is designed in Italy, a member of a secret order of Trappist super taster espresso engineers comes in, sets up the pressures, the jets, the basket and dose sizes, and then leaves without a word ...

in any case, rotary machines are set to 8 to 9 bar in Italy, and vibe pumps at around 10 to 12 bar. I was conflating the two when I wrote the guide, since I thought a properly OPVed vibe was identical to a rotary. But I think the initial attack of a rotary that Dan described may make a difference. Certainly on my Elektra, which runs at 11 to 12 bar, adding an OPV made no difference at all.

I don't have taste evidence. But Ken, who has identical vibe and roatary Cimbalis, needed a delay-on-make preinfusion relay on the rotary, but nothing on the vibe.

It could be that overpressure ruins the shot in the first few seconds.

Now, I do have ~3s of line pressure preinfusion (via a delay timer relay) and a smaller-than-standard gicleur on the grouphead (The Keihin motorcycle carb jet, #68). I am sure that technically these don't do much for getting the machine in the range of a water debit that would match a double boiler with a proper gicleur, or a vibe pump machine, so the pressure ramp-up is still quite fast, and I am sure that the added pressure aggravated that.

The pressure ramp up/excessive pressure during the shot most certainly ruined a lot more of my shots from a simple visual perspective. Maybe you're right--maybe even the ones I thought looked good were also extracting wrong. While the naked portafilter can sometimes give TMI and give the impression of defects in a shot that's actually quite tasty, it can also give the false impression that nothing's wrong. At a basic level that was obvious enough to me when having fine-looking shots that tasted about as bad as the ugly pours.

I guess with these thoughts I can believe/understand what happened more easily. The Elektra strikes me as a machine that's exceptionally forgiving when your parameters are within her range (dose in particular), but certainly stepping out of those can lead to much groaning and gnashing of teeth. I guess that's the ticket I bought myself when I broke my gauge line and left my pressure regulator wide open.

Hi Nicholas,

glad to hear things are back to normal. One thing though

Now, I do have ~3s of line pressure preinfusion (via a delay timer relay)

Does this pre-wet the puck entirely (I doubt that)? After various experiments with preinfusion I now abandoned the whole concept as I don't think it gives you anything. I'll say even more, I think it can cause more bad then good, especially when it soaks the puck only partially. Anyway have a go at no preinfusion and see for yourself.

Regards,
dsc.