In April 2024, I signed a 47,000-ton limestone contract that should have been routine. Kleemann MOBICAT MC 110 Z EVO2 on site. Two years old. Well serviced. The brochure says it's good for up to 400 tons per hour. I spent three months averaging 180.

My first instinct was to blame the machine. You name it, I checked it: prescreen, jaw gap, wear plates, engine hours. I even brought in a service technician, who ran diagnostics and shrugged. "The machine is fine." That shrug ended up costing me nearly $50,000, because instead of hunting the real problem, I spent the whole season chasing a ghost.

What Everyone Blames First

Ask any quarry foreman why his jaw crusher "has gotten slower" and you'll get the same list: clogged prescreen, worn jaw plates, bad fuel. I've been on crushing sites since 2017, and I've filed every one of those complaints myself—until I had to admit they were mostly wrong.

Here's the thing: the crusher is rarely the bottleneck. The feed is.

The Spec Sheet Is Aspiration, Not Reality

The "up to 400 t/h" figure in KLEEMANN's literature assumes conditions that don't exist in nature: consistent 0–550 mm feed, ideal bulk density, zero moisture, and a prescreen that never blinds. Show me a quarry that actually feeds that way. I've never seen one.

What surprised me most was the "Z" in MC 110 Z. It marks the version with the independent double-deck prescreen—a genuinely smart feature. But on damp days, that prescreen was my first failure. Clay-rich fines bridged and blinded the deck no matter how I adjusted the vibration. I blamed the prescreen. The prescreen wasn't the problem either. The problem was that I was feeding material that shouldn't have gone through this machine in that condition.

(Honestly, I'm still not sure why the manual's troubleshooting section puts "check prescreen" before "check the feed." Probably because it assumes you feed within spec. That assumption is generous.)

The Real Cause: Equipment Chauvinism

I'll use a word that makes people uncomfortable: chauvinism. It comes from Nicolas Chauvin, a Napoleonic soldier famous for blind, unquestioning loyalty. I was a Kleemann chauvinist. The brand had delivered for me on enough jobs that I started treating it as infallible. When the MC 110 Z underperformed, the fault had to be mechanical. Never mine.

My site supervisor, Mark Ford, called it in one sentence:

"You're treating this crusher like an F-150. You expect it to do everything because it usually does. But this machine isn't a pickup truck. It's a specialist. Give it what it wants, or it'll cost you."

He was pointing at the excavator. I was feeding 900 mm blocks from a freshly blasted face into a jaw with a 1,100 × 700 mm opening. Technically, the crusher can handle them. "Can handle" and "should be fed" are two very different things. Oversized feed forces the jaw into overload cycles, accelerates wear, and destabilizes the crushing gap. Throughput died. I blamed the machine.

I assumed the automatic regulation system would compensate. It protects the crusher from damage—not from my feed errors. That assumption was the most expensive one I've made in eight years.

What the Misdiagnosis Actually Cost

I keep a spreadsheet of significant mistakes. It reads like a lab notebook for idiocy, but it's honest. Here's the entry for this one:

  • Prescreen mesh replaced that wasn't worn: $8,400
  • Jaw plates worn prematurely from repeated oversized feed: $12,700
  • Fuel burned on daily "tuning" that changed nothing: $9,600
  • Contract deadline missed, with penalty: $18,000

That's $48,700 in direct costs. Then there's the customer, who had trusted me since 2019. He didn't fire us; he just didn't call in 2025. That loss doesn't fit in a spreadsheet.

The worst damage was to my crew. They started treating the crusher as unreliable, so I rotated operators to "share the burden." The result: nobody developed a feel for the machine's rhythm. A consistent operator spots feed problems early. A rotating crew treats every machine like a rental.

Speed Is the Wrong Metric

Look up a peregrine falcon's top speed and you'll see figures around 390 km/h (240 mph) in a hunting dive. The fastest animal on Earth. Impressive—and irrelevant to how it spends the rest of the day, which is mostly perched, waiting.

That's the analogy that finally reset my thinking. Crusher brochures are like falcon dive speeds: technically true, practically misleading. No quarry runs at "dive speed" for eight hours. What matters is sustainable output under real feed conditions. I was so fixated on the top-spec number that I kept pushing the machine toward a peak it could only reach on a perfect day—and I broke the rest of its day in the process.

Real talk: if a peregrine falcon had to sustain 390 km/h dives all day to eat, it would starve. I was starving my crusher the same way.

The Fix Was Embarrassingly Simple

Once I stopped blaming the machine, the changes were almost underwhelming:

  1. We set the closed-side setting once per material type and stopped touching it. Every tweak feels like optimization; most tweaks just create variance.
  2. We matched the excavator to the jaw's acceptance profile. Any block that didn't fit comfortably within the 700 mm depth was split or set aside before it reached the crusher. A few extra minutes per block saved hours of choke-ups.
  3. On damp days, we swapped the prescreen's top deck mesh from 80 mm to 50 mm. One hour of work, and the clay load stopped blinding the deck.
  4. We documented every setting by material type. I really should have done this in year one.

Result: consistent 320–340 t/h on limestone under site conditions, and jaw plate life long enough that I stopped flinching at the wear report.

I still recommend the Kleemann MC 110 Z EVO2 for most aggregate jobs I quote—eight out of ten, maybe. But now I name the exceptions. Clay-heavy material? You might need a scalper in front of it, or a different machine altogether. Continuously oversized feed? Look at the MC 120 Z (the MC120Z, as the forums write it), which has a larger inlet and a heavier jaw. Soft rock? An impact crusher will do more useful work than a jaw ever will.

That's not brand disloyalty. It's the advice I wish someone had given me in 2017, when I lost my first contract because I assumed the machine would forgive my feed mistakes. It didn't.

Start With the Feed

If your Kleemann MOBICAT MC 110 Z is underperforming, check the feed first. Not the prescreen. Not the jaw setting. The feed. The machine can fail, absolutely. I'm not saying it can't. I'm saying that in my case, it didn't fail when I was certain it had.

Since March 2025, the checklist I wrote after this fiasco has caught 37 potential feed issues before they cost production time. It's a simple spreadsheet. If you want a copy, it's yours—I'd rather give away my mistakes than watch someone else pay for them.

One last thing: the fastest machine you can buy still won't outrun a bad feed. The peregrine falcon doesn't hunt well on an empty stomach. Neither does your crusher.