I just picked up a Bunn G1 which I tore down, cleaned, and reassembled. I have a few questions:

Retention

- Some of the grinds end up back in the area behind the burrs by the auger as in the photos below - is this an expected amount? Is there anything I can do to reduce the amount?



Bushing

- Is this the bushing that the parts diagram calls out as Item 6 (05870.0000) in the burr housing diagram? It doesn't come out - how do you remove it?



Burrs

- I currently have the stock burrs that came with the grinder, and I seem to get quite a few fines. How do they look in the photos below? They don't look or feel particularly sharp to me, but this is my first flat burr grinder.

- I plan to replace the burrs at some point with SSPs; the 80 mm burrs they list at espressotool.com are listed as multipupose. Are the 80 mm burrs available in a filter-specific geometry that would be significantly better than the multipurpose geometry? And about the coating - anything to choose between the Silver Knight, Red Speed, and TiN options?



Thanks - I appreciate your assistance!

I don't have particular experience with Bunns (I did cross-shop them heavily), but the architecture is a lot like the EK...

1. Looks like typical schmutz for a grinder that's seen hard commercial use and wasn't particularly cleaned well. If you keep up with cleanings every 3 months or so, plus the vastly lower volumes of home use, you won't see anything like that buildup in the future. If you haven't looked at the tutorials for polishing the output chute, do that.

2. Wow, that's a tight fit. On the EK I can pull out the distance bushing with a pair of duckbill pliers, there's a ton more room there (may be a good or bad thing, depending on how you look at it). If you're doing a clean, I would probably pull the motor entirely and then you can use pliers or a puller tool to separate the bushing from the motor shaft.

3. The official line is that "Red Speeds are for espresso, Silver Knights for filter", but there are enough people who have tried both in their Monoliths and EKs that seem to get identical results using either (given the same burr geometry). Silver Knights are supposed to be a harder surface, but in home use the burrs are rated for so many pounds before needing to be sharpened that it's irrelevant. As far as burr geometry, do you ever see yourself trying to dial in espresso with this? I know for something like an EK or a Kafatek it's a valid concern, but even with the detents epoxied over like some have done, the stock Bunn threaded adjustment is a PITA to try to dial in 'spro. I'd say get filter-focused burrs...

Not sure how long it's been since the grinder was cleaned, but Bunns aren't known for low retention. On my Bunnzilla, there are grinds pretty much every place there's space (which there are a lot). It's just a weakness of the grinder. Doesn't look unusual, especially if it hasn't been cleaned for a while. The only thing I could do to noticeably reduce a little retention on mine was smooth out the exit chute. It's soft metal that can easily be sanded. It's bumpy and rough from the factory. There are several old posts and pictures if you can't picture the area I'm talking about.

Your picture does show the bushing - it's almost like a washer around the motor shaft. Be careful if you do remove it as you don't want old coffee grounds to end up behind it or under it. I didn't remove mine but you might need to take the entire housing off? Can't help too much there.

I have the SSP Silver Knight burrs. They're good but I never tried the stock burrs in mine since they looked 20+ years old and rusty. I chased alignment for a while via sanding and shims but could never get it too great.

Enjoy the grinder - it's a great purchase for the money.

Thanks for the replies!

These photos are after I tore it down, cleaned, reassembled, and ran some beans through to flush it out - I took these photos to show the amount of grounds that end up back in the auger area. I'll consider sanding the exit chute - probably when/if I do the sandpaper alignment with the new burrset.

I'm glad the bushing is there - it wasn't coming out without unbolting the grind chamber from the motor (which I don't really want to do as I'm concerned about messing up the alignment); I just wasn't sure if that was the bushing or if it was missing.

About the SSP burrs - I don't plan to use this grinder for espresso much at all as I have other grinders for that, so I was wondering if SSP offered the brew-specific geometry in their 80mm burrs as they only list the multipurpose ones. I'll likely opt for the Silver Knight coating.

This is a fun project! I'm not impressed with the results just yet, but I think (hope) it's due to worn stock burrs, and things will be much improved with the aligned SSP burrs.

I recently went to the SSP Red Speed burrs after having the stock Bunn burrs for about 5 years. In my opinion, there is a huge difference in the grind/cup quality. The stock Bunn burrs produce relatively consistent grinds but way too many fines for brew. The new burrs give me great cups with tons of clarity and flavor separation. I recently got an Orphan Espresso Apex and I think I prefer the Bunn with SSP burrs. I still need to experiment more with the Apex though. The Bunn with SSP burrs produces quite a bit less fines than the Apex and that really affects the draw down in my v60. I'm waiting for some Cafec filters to arrive to hopefully even the playing field.

The 80mm SSP burrs are only suitable for "modern espresso" in my experience. Even with the burrs set to as fine as possible without touching, the shots pull really fast. Not traditional but seem to taste good no matter what.

jayo wrote:These photos are after I tore it down, cleaned, reassembled, and ran some beans through to flush it out - I took these photos to show the amount of grounds that end up back in the auger area. I'll consider sanding the exit chute - probably when/if I do the sandpaper alignment with the new burrset.

Could be the worn Bunn burrs causing some of that retention. Also if you don't give the beans a spritze of water before dumping them in you will get a lot of static which can add to the retention. I'm still using the Ditting 804 machined burrs I installed back in 2010. I run 40g of beans through every morning for our vac pot brew & retention is minimal. I did clean up the exit chute area years ago which helps some. Took a look inside for the first time in ages this afternoon but there wasn't much to see. Nothing on the burrs, a little pile between the auger tunnel & fixed burr center, nothing much in the tunnel & just a thin coating of coffee dust on the exit area.

Thanks for the input on the upgraded burrs - I look forward to the upgrade!

Has anyone gotten brew-specific geometry in the 80mm SSP burrs? I've filled out the contact form at http://www.espressotool.com/20, but I haven't heard back. It may be moot anyway, as it seems everyone is happy with the multi-purpose burrs for filter in their Bunzillas.