I've cleaned and refurbed a handful of majors and never had a single issue. The latest one is very puzzling - especially as it is cosmetically in much better shape than the others I've worked on and appears to be a of a bit more recent vintage.

I did a deep cleaning, installed a set of replacement burrs (I usually test the existing burrs first but the set that was in there even felt worn out - in addition to looking rounded and worn.) The replacement burrs were an older set of non-OEMs that I had in the drawer but have never been used and I've used other sets from that batch in previous grinders and never had an issue.

Here's the deal: it starts, runs smoothly and quietly, and I can easily find the point where the burrs touch (can even stall it by going a bit further.) When I add beans they just popcorn and get coarsely crushed inside the grinder throat - they never go all the way through and no grinds come out.

I tried shifting the upper burr by rotating it 120 degrees and re-securing the screws but still no luck.

Any ideas?

Are you sure it's turning in the right direction?

That's the first thing I confirmed. It turns in the correct direction - same as every other Mazzer grinder I've had. Second thing was to ensure that the burrs have the cutting edge facing same way as the original burrs - that is also a check yes.

I was advised to check burr alignment by marking the flat top edge of one burr with felt tip marker, reinstall, run grinder, tighten down, and then check to see if the black area is completely worn off or instead if part wore off and part did not. I did this and there is a small area where some black remains. I can see how this would affect consistency of grind quality but at tight settings it shoudl still be feeding beans through (by the way - I also checked for obstructions in the feed chute that goes out to doser and it is clear.)

I sold a major recently, and the buyer had a similar problem. It turned out that they were trying to dial in the grinder with old, oily beans, and those beans were clogging the output chute. They changed to fresh beans, and the problem went away.

Could it be a bean problem, and not a Major problem?

Randy

Unlikely to be the beans. I'm using a Brazilian Mogiana natural - roasted to a moderately light level several months ago and frozen immediately after roasting. IT didn't turn out to be a good fit for the espresso blends I was developing, and has been set aside for grinder testing. Dark, oily and old beans never darken my doorstep. Having said that, I will also mentioned that I've even purchased grocery store whole bean coffee (Eight O'Clock Colombian) for grinder testing and never had an issue like this before. This same coffee grinds perfectly in the SJ that I am using for my own espresso, as well as in another Major I compared it to last night.

The "nothing comes out" comment is a puzzle.
I assume you tried a very-much more coarse setting...?
I would start by trying another set of burrs.
Did it ever work properly before you did the refurb?
Are the grounds ejection fingers pointing in the correct direction to properly sweep?

I tested that it started and ran before I cleaned it... and there was a bunch of old grounds in the doser chamber - it was definitely working before it was taken out of service. I hate to break the seal on a new set of Mazzer 83 mm burrs just to test... but your iodea is a good one. I'll pull the burrs from another Major and try those instead (I have also now modified my routine to include testing with beans before I tear these down for cleaning.) I don't follow you on the quesiton of the ejector arms - they are indeed directional but are an integral part of the circular base plate under the lower burr, and this plate appears to be original equipment with this grinder.

Thanks to all for helping with the brainstorming. I'm gone for the weekend but will get back to this Sunday night and post my progress (when I do have some to report!)

Phaelon56 wrote:..... I don't follow you on the quesiton of the ejector arms - they are indeed directional but are an integral part of the circular base plate under the lower burr, and this plate appears to be original equipment with this grinder....

My thought was that someone who had it before replaced the plate with one made for the opposite direction of rotation... if such a thing even exists.

Sometimes too fine stops any coffee exit. Macaps come shipped that way.

I had exactly the same problem when I accidentally tightened the grind without the motor running on my old Macap M4. It just chewed up beans in the throat, and nothing came out of the chute. I had to open it up and scrape the compacted coffee off the burrs.