Underdeveloped Roasts


Well, I’m roasts in with the Bullet after having used a popcorn popper and then a Hot Top. And like others posting here, it was beyond frustrating from having produced great roasts to having produced lackluster roasts. The learning curve is high. I had the additional issue of a defective bean temp sensor until I was upgraded. Having said that, I am now producing good coffee…but not great. I will post a couple of profiles later both for guidance to others but also for a discussion/suggestions about how I can improve my roasts. I roast Ethiopians pretty exclusively. I do make an Ethiopian espresso for my daughter but most of my roasts are FC to FC+.

Look forward to everyone’s input and thanks in advance. I have tried to copy a profile to insert here but unsuccessfully. Please let me know how you do it (for those who have attached their profiles).


Hi All,

I struggled with similar issues when I first got my Bullet.
I am roasting on a V1.5 with calibrated fan speeds. (Indoors)
My first big jump to better roasts and smoother RORs happened when I lowered my drum speed to D6.
I only roast 454grams (chargeweight) and D6 seems to be the ideal speed in my setup.
I usually charge at 250C (482F), lower the Power to P0 as soon as I charge and raise it at turnaround (ca. 1:10min) back up to P9.
Then I gradually lower the Power and increase the fan speed.
Here are my milestones (all temps are IR sensor)

Charge and lower temp to P0 until turnaround then P9 D6 F1
145C … P8 D6 F2
165C … F3
175C … P7
180C … P6 F4
195C … P5 F5 (this is in anticipation of the exothermic reaction at FC)
203C … P6 ( to avoid ROR crash after FC)
206C … P5
210C … F6
213C … P4
214C … P3 F7

You can put all this in a recipe, but don’t forget to add a time condition of 1min to each temp condition.

For example:
Bean temp is 145C AND time elapsed is 1 minute.
ALWAYS use 1 min, otherwise the recipe won’t run.

I usually drop my beans right around 215C.

Also, wait a couple of days until you try your fresh roast.
The beans seem to be “developing” their real flavor while they are resting for several days.
I usually wait about 4days and can recognize a strong improvement up to about the 14day mark for most of my Roasts.
Yemeni roasts seem to benefit from an even longer wait (2 weeks) after roasting.

Have fun!


Just wondering here, could your brewing/grinding method be the culprit? Have you tried to buy some store bought specialty coffee to compare?

I’ve done 15 roasts on my V2, and have gotten nothing but great results using the standard beginner’s profile from the manual (preheat to 230C, then gradually decrease power & increase fan speed). Also all my roasts look “Rao approved” naturally, with the declining RoR curve.


Wanted to add my experience here as well, since similar to others, I had 9 months of a terrible time with the Bullet and now have great(amazing?) results. I used to have a Behmor where the same beans worked beautifully, whereas in the bullet I choked every morning on my espresso. A disgusting time I don’t want to look back.
The issue is that there are so many knobs on the Aillio and I had no systematic way to approach them and no theory behind me (I only saw this thread here now)

A lot was mentioned already, but wanted to summarize my approach here which took me from terrible to amazing:

  • changed batch size from 500g to 350g ( I do 2 batches back to back now)
  • changed preheat from the default 200C to 220C ( that has a tremendous impact). I also let it preheat for a longer time. I have no system as I do other stuff but it sometimes approaches 45-60min preheat time.
  • rather than playing with power settings I mostly do fan speed. I adjust power ±1 at most during the roast but mostly keep it at P6
  • I do a lot with fan speed - I used to have only F2 - but now do F4-5 as default and regulate up or down. If I feel temp change slows too much I lower the fan speed a little when temp rises too much I raise fan speed.
  • There is actually impact from the drum speed. I have my default now at D6, not the D9 which I can test the difference
  • Changed my beans. Lastly I changed my Ethopian batch which just didn’t work on the Aillio but was phenomenal on the Behmor.

I do only SingleOrigin and for 2 months have had amazing results with these adjustments with different beans SM-YEMEN, SM-Burundi, SM-Polar Expresso.

I didn’t see this thread, but what triggered most of my changes was a notion that I read I need to let the beans develop after yellowing. That’s for the most part what I do now. I have lots of momentum in up to yellow and then take a little out and even more so when it reaches first crack where I take all out ( lower power and increase fan ) and then push up again (higher power - lower fan) when then RoR goes below 5.

You guys are way more experienced. I only roast for 3 years overall and 2 only on the Behmor and have no theory behinf me, but the above really worked for me. Oh, the roast curves between terrible attempts and amazing ones are not that different in my opinion. When I look at mine anyways. There seem to be very subtle changes that make great coffee and really don’t show up in the graphs. ( to some degree they do by reaching a certain temp 30s earlier but it’s subtle)


Same EXACT experience here. Went from great coffee to an occasional hit and i"m on about my 30th roast with the bullet. Development is certainly the issue. I’m honestly really frustrated also. ITs an entirely different beast. I also don’t think the temperature probes actually read anything accurately. I believe actual bean temp to be right in the middle of the 40º spread between the 2.


very interesting. I’m in the same boat. Realizing I need to change the development. And same bean selection,. Love the SM yemen, guji, etc. Went to gagging on my espresso from loving it. Thanks for sharing the info!


I do 1KG roasts and have been strictly adhering to the declining ror method. I’ve been preventing the flick just before FC by decreasing the power and continuing with that setting for a while after FC. After reading a recent comment by Jacob on another post where he pointed out a momentary decline in the irbt curve after FC despite a really smoothly declining ror curve, I pushed up the power right after FC to prevent the IRBT curve from declining and that helped speed up my roast and improved the development of the beans.


I’ve stuck with it, continuing to roast, refine my experience and learn. I bought a 50 lb bag of Kenyan AA (my favorite), and have stuck to the maxim of only adjusting one variable at a time. I’ve incorporated a good deal of the general advice on this thread and it’s helped tremendously. My results certainly aren’t as good as my favorite local/professional roasters, but I’m roasting some coffee that’s really quite good.

From my personal experience and reading that of others, I’ve developed a theory that the Bullet needs much more seasoning than advertised. To a new user, I’d suggest he should expect to roast 20 batches before achieving any quality in his roasts. It took me at least that. But now, I’m enjoying the coffee I roast and continue to study the process. It’s been very rewarding!


I agree with you about the persistence of unimpressive roast flavors beyond the recommended seasoning roasts.

I looked back at old comments on my RT charts and the piles of unroasted coffee that were ignored because the results weren’t worth repeating at the time I bought them. I’ve gone back and tried a few and today I find the product is pretty darn good with the same or similar profile. I think I mentioned to you in January that I was really unhappy about some Kenya I bought in early 2019. In Feb I tried the same Kenya again and can’t believe how much better it tastes with the same profile; when I switched to my current approach, I managed to get something even better.



Thank you! I ran this today, and will brew it in a couple days. You have a few different variables like the soak and higher charge temp, but you’re saying the real noticeable change in development happened when you slowed the drum down?


Hi Colin,

I always had issues with ROR.

Very up and down.

It felt like whatever I did with my powersettings or fan speeds did not have the desired effect.

Or let’s say I just overshot ROR vise in both directions.

When I finally reduced my drum speed from D9 down to D6 I started having way more control.

I also use old greens (about 300g) for “seasoning” before every roast.

My startup regime is:

30-40 min preheat (I just close the door so I won’t hear the continuous “charge”)

Then around the 40 min. Mark I go through one actual roastcycle with my old greens (millcity roasters supply them) and after that one I go for it.

YT around 4:30

FC around 07:30 to 8

Drop around 216-220 C (ibts)

All very repeatable.

Hope this clarified things a little more.




Here is a SM Papua New Guinea which I roasted 3 days ago.
Tried it this morning (Hario Drip, 4 min.) and it turned out quite lovely.
I am sure it’ll even get better over the next week or two.image


Ok that makes sense; thanks for the tips! It can feel like a vehicle that’s gone out of control, especially in the last third of the roast.
I tried the coffee from the above recipe and it’s very good. Thanks for that!
I’m wondering if my roaster isn’t fully seasoned yet. I’m at around 30 roasts and I’ve been consistently getting soapy notes and dryness on the tongue as the cup cools. With my last roaster I didn’t experience that.


Your thoughts on seasoning are probably spot on.
Here is a Yemen I tried this morning after 5 days of gassing out.
Very promising. Usually I don’t go up to 220C for my drop temp., but this one might turn out to be a bomb.



If I wanted to take this to 2nd crack would you just preheat higher or would yo suggest extending the temperature triggers by a couple degrees each from first crack?

thanks for your advice



I’d do a couple of test runs with higher preheat (260C or 270C)otherwise you might stall the roast.

Then on the other side this might shorten your Drying and Maillard phase.

I think a little more momentum in the beginning wouldn’t hurt to reach the “Dark Side”.

Not sure about extending the triggers.

This might get you into baking territory.



Thanks for the suggestions. I’ve had problem stalling the roast. I’m trying to hit 228c but the last third of my roast is as someone else said “a wild ride”

I will try your triggers and a little more heat tomorrow


This is a good question that I’ve been wondering as well.
If I want to go past 2C using a nice descending ror, I usually hit the ground about 2 mins after 1C and am forced to run along the ground flatlined and baking.
If I raise the heat at the beginning to give me more height to work with, I’ll probably hit 1C too soon, which I’m guessing is a bad thing. Let me know if you have any success in your experiments.


I made a recipe using 260ph but had to use F2 to keep from getting the A-01 error. Looked good for a long time but ran out of gas at about 10 minutes. Had to go really far to get 226 degrees and second crack started while dumping. Maillard a
was less than I like as warned would be likely.


In my experiences I find cutting the power and raising the fan too high at the same time will stall the roast. I think raising the fan is great for developing the interior of the bean but I would have stayed in the power a bit longer before cutting it.