Many users of the BCG800XL SmartGrinder experience jamming / clogging and a horrible gear-stripping, clacking sort of sound during use at some point.
Here's a 10-second video I recorded of the problem / symptoms:
This is usually either a '''worn out impeller''' or '''stripped drive gear'''.
The main symptom of a worn impeller is the motor will bog down even at a coarse grind settings (which should be easy on it) and after a few seconds, after too much coffee gets compacted beneath the burrs, it begins making that stripping / clacking sound you hear at the end of the video. When the hopper is empty and no beans are in the burrs, it all sounds great. You can even hear in the video above: The unit starts out sounding normal, but under load, up until the clacking sound. Often, incorrectly, the coffee beans get the blame.
On the other hand, a stripped drive gear will sound bad nearly ALL THE TIME, even with no coffee beans. Each revolution of the damaged gear teeth will make a bad sound. If the teeth are really wrecked, you sometimes won't even get rotation anymore and you'll just hear the motor spin up like a jet engine. Thankfully this failure mode is much less common; typically occurring if you got a rock or pebble jammed in the burrs during grinding.
Now, why does the BCG800 Smart Grinder's impeller matter? It sits underneath the steel burrs and receives the ground coffee. Its purpose is to push those grounds out the chute that leads to the basket (or espresso portafilter). When the plastic blade fins wear down over time, the grinder begins to clog up because it can't properly expel the grounds anymore. This often gets mistaken for a problem with the main drive gear when a stripping sound comes from a torque limiter mechanism. You can examine your impeller if you simply remove the burrs, and look at the gap between the cylinder wall and the impeller blade tips (See the good vs bad pics in step #1 below). If that gap is more than 1 mm, then it's probably worth replacing. If you can take the impeller out without dis-assembly, then it's definitely worth replacing (A good impeller is wider than the hole and can't just come out).
Breville unfortunately doesn't sell parts, so this tutorial has been made possible only recently by 3D printer technology. I've designed an improved impeller for the BCG800XL and made it available here: [https://www.shapeways.com/product/NASLAGCCP/breville-bcg800xl-coffee-grinder-impeller-upgrade?utm_source=ifixit.com&utm_medium=referral&utm_campaign=ifixit_bcg800xl_impeller|Shapeways Impeller Source]
Here's a quick two minute overview of this replacement part:
This guide will walk through impeller replacement to fix the most common cause of jamming with the BCG800XL (and BCG800) Smart Grinder from Breville.
'''If you prefer a full length video walkthrough, equivalent to this guide, then the video below will do the job (Duration 20 minutes):'''