Smoke coming out from front panel and bean charge chute

I have been having a problem the last few days with smoke bellowing from the front panel of the bullet during the roast (this has never happened before) and I notice at the end of roast when I check the bean charge chute, a lot of chaff is stuck there (hardly any in the back chaff collector) .

Has anyone experienced this before and could it be do with my exhaust adaptor and duct piping?

Thank you!

You might make sure there is only a loose fit or an air gap between the Bullet’s exhaust and piping. It sounds like air is being blown into the Bullet rather than exiting it properly. If you don’t already have one, an inline exhaust fan can help keep the air moving in the right direction during roasting. Also, make sure the chaff collector and impeller fan are clean/free of debris to help ensure they are working correctly.

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You might want to read this thread. It could be something stuck in your exhaust.

Long brush for cleaning the air transfer tube and bean chute - Taking Care of the Bullet R1 - Roast World Community

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Prob the chaff filter is blocked or the exhaust fan is not operating (e.g. F=0 or the fan is not spinning) or the exhaust fan is just not spinning fast enough…

  • Check the chaff collector and the rectangular-ish transfer tube from the front (behind the bean chute) to the chaff collector.
  • with the chaff collector off confirm the exhaust fan (lines up with the chaff filter) is operating, Probably better to view it downward thru the exhaust port during a roast/fake roast or during preheat to confirm the fan is spinning.

The exhaust fan is sensitive to adjustment of the ‘muffin’. Either too far onto the motor shaft or too close to the tip of the shaft will cause mechanical interference and stop the fan (the latter instance will contact the filter basket; the former will contact the metal behind the fan.

When you check the transfer tube you’re looking for beans and/or chaff filling the tube and blocking air flow.


I think it could be air being blown back through, I will re look at my set up today and see! Thanks so much

what do you mean by the muffin sorry? Thanks for your reply!

I have checked the fan and it looks to be running fine during roast (not too close to the metal or rubber) so now I’m really stuck as to why!

If you want to check that the fan is working, you can run a roast without beans and turn the power down to zero (no heat) Then change the Fan output up and down and hold your hand over the exhaust. You should be able to feel a difference in the amount of air coming from the exhaust. This is not very scientific, but will allow you to verify that the fan is working.
Have you calibrated the Fan?

Also, if you hold the filter screen up to the light, is the mesh clean? can you see through it? There was a thread on the forumn where someone shared a photo of their screen filter and the screen was almost completely blocked with a tarry substance.
I use Cafiza to clean the filter screen on my Bullet. The Cafiza won’t hurt the stainless steel fileter screen.

Sorry if these are things that you have already checked.

The impeller on the exhaust fan is a ‘muffin fan’… a cylindrical affair with horizontal blades.

Too much info. Sorry. Try what @billc suggested- a dummy roast with P=0 (P0). That way you can watch the exhaust fan behavior without heating the roaster unnecessarily.


While doing that, you could activate the info panel and change fan speeds during mock roast to see if the RPMs are correct.

Please take out the chaff filter and post a photo of it.

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Tried cafiza, it worked a treat!! It is roasting as normal now. Even though I thought it was clean, it must have had residue oil still.

Thanks so much for your help.


An alternative to Cafiza is Sodium Percarbonate powder. It’s less expensive than Cafiza and cleans the chaff filter up quickly so it looked brand new. It’s also used in a lot of laundry and dishwasher soaps.Thompson mentioned cleaning with Sodium Percarbonate in one of his videos. It works great on lots of materials but will tarnish aluminum such as the fan blade. We liked its performance so much we have used it for a lot of other things including our silverware and found a laundry detergent based on Sodium Percarbonate. We also use it in our dishwasher without a problem.


I use Urnez Tabs to clean my coffee pot and I’ll briefly (5 minutes or less) soak the impeller fan and chaff filter basket) in the hot liquid from my coffee pot to clean them of oils.

I ended up getting a second chaff filter (and gasket since the second one was loose in the original basket) so that I can swap them out between roasting batches.