Many users of the BCG800XL SmartGrinder experience jamming or clogging and a horrible [https://www.youtube.com/watch?v=8tCumd7M7Uw|gear-stripping, clacking sort of sound] during use at some point. This is usually due to a worn out impeller or -less commonly- a stripped drive gear. This guide will show you how to inspect the and replace the impeller when it is bad.
Please review the [https://www.ifixit.com/Wiki/Breville_BCG800XL_Smart_Grinder_Troubleshooting?revisionid=HEAD| Breville Troubleshooting page] first to be sure your grinder does indeed need an impeller replacement.
Breville, unfortunately, doesn't sell replacement 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-coffee-grinder-impeller-upgrade|Shapeways Impeller Source]
[https://youtu.be/zB5F9ha1-zs|Here's] a quick two-minute overview of this replacement part.
This guide is for the BCG800. If you have a BCG'''600'''SIL or BCG'''400'''SIL then [https://www.ifixit.com/Guide/BCG600SIL+Grinder+Jamming+due+to+Worn+Impeller/96493|go here instead].
Update 11/19/18 - Breville has upgraded this model to the BCG820XL which uses a different sized impeller. While it is covered in metal, it is still plastic underneath and will wear out if you are using it for espresso rather quickly. The impeller used here will not fit. I trimmed down the shapeways impeller referenced here with a dremel and it still jams. It is possible to disassemble the grinder, but replacing the worn impeller is currently impossible. I have included comments for disassembling the BCG820XL.