Thread Number: 36731  /  Tag: 80s/90s Vacuum Cleaners
Kirby Tradition Fill-tube design flaw?
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Post# 393001   6/8/2018 at 12:12 by rowdy141 (United Kingdom)        

Kirbyís initial attempt at a disposable-bag system (Kirby Tradition) was reputedly flawed by an undersized fill-tube. This supposedly restricts airflow, causing a bottleneck and loss of efficiency. The common remedy is to change the em-tor/tube assembly for one with a larger diameter.

Iím wondering whether this is a false impression, or perhaps limited to USA models?

I canít see design engineers at Kirby making such an error; they had a blank canvas to design these and must have experimented with prototypes. I suspect they deliberately chose to make the tube narrower than the ducting because when air flows from the fan and reaches the smaller-diameter fill-tube, it increases in pressure, moves up the tube faster, and carries heavier particles with it. When the air reaches the top of the tube, pressureís reduced, and the particles fall into the bag.

Machines manufactured for export (UK) donít have fast/slow motor speeds. Ours run at high speed all the time, for both brushroll-head and hose. Could this modification be more applicable to USA models where the fan speed was slower?

Newer, wider fill-tubes (Heritage onwards) occupy more of the space within the cloth bag, so paper bags now need replacing more frequently. Consumables, as we know, have the longest return profit wise.

Post# 393004 , Reply# 1   6/8/2018 at 13:43 by dysonman1 (Missouri)        

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The Tradition's horrible fill tube reduced airflow tremendously. One almost has to put the height setting on #1 to get it to clean anything. Yet the motor is identical with the Heritage - but the Heritage has double the airflow. The only way to make a Tradition clean well is to fit a mini-emptor and Heritage II fill tube and bag adapter.

Post# 393008 , Reply# 2   6/8/2018 at 15:42 by rowdy141 (United Kingdom)        

Thanks Dysonman1,

That's the first time I've heard this problem described in that way.
I think you're confirming my suspicion that UK machines may not need this mod. because I don't have that suction issue with the original Tradition set-up. Mine goes like a tornado and sticks so firmly to carpet, that I cannot literally push it along on closer settings (and I'm a 6' "brick-outhouse" guy). Same with my Legend II.
I can't detect much difference between them. These are 240v UK models, permanently on high speed. Is that the reason? Has anyone Stateside tried the original Tradition fill-tube set-up and switched their motor to Hose speed?

Anyway, I ordered the larger fill-tube (£15 fron ELI) and I'll be modifying my Tradition to see how it goes. Open to the idea that this may be an improvement for me.

Post# 393010 , Reply# 3   6/8/2018 at 16:48 by Kirbysthebest (Wichita, KS)        

It was explained to me, and I worked for Kirby during the Tradition run, that the reasoning behind the smaller fill tube was to throttle down the air flow, because the single ply Type 1 bags were unable to handle the full air flow.

Bag material and fill tubes have improved since then, however, the Tradition was still a good cleaning machine.

Post# 393012 , Reply# 4   6/8/2018 at 18:01 by Ultralux88 (Denver, Colorado)        

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Set three Kirbys up together, the Classic 3, Tradition, and Heritage, Turn them on one at a time, both with hose and with nozzle. Compare the way they sound, compare the suction, and you'll see the airflow loss, and how the change to the larger hose on the Heritage really made all the difference.

Post# 393031 , Reply# 5   6/9/2018 at 00:28 by tolivac (Greenville,NC)        

The problem I had with the Tradition fill tubes is they were always rotted out on any Tradition I have--so you have to replace the fill tube with a newer wider one.Plus you have to replace the gasket on the emptor door.

Post# 393475 , Reply# 6   6/18/2018 at 10:58 by tommymilan (milano)        
In Italy

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Dear all, I have two Kirby Traditions, one from 1979 and one from 1981: both of them have two speed motors, one came with the shake-out bag, the other with paper bag fill tube and the original bags with horizontal oval opening. I have always wondered the reason of such a small fill tube and such a weird top bag adapter. My choice was to purchase a fill tube assembly for the Heritage, then replace that weird flexible pocket-like filling system as well as adapting a round top bag adapter that allwoed me to use Microm magic bags.
The difference was more than noticeable, I'd say just amazing!
Greetings to all!

Post# 393483 , Reply# 7   6/18/2018 at 17:29 by Rowdy141 (United Kingdom)        

The new, stronger, bags probably negate that issue now, as you say. Luckily, I have TWO Traditions now, so I'll be experimenting, while still keeping one machine all-original.

I'm not really doubting what others have said, I'm sort-of 'Playing Devil's Advocate', questioning it all, trying to understand the science.

Am I right in thinking air flows more slowly in wider tubes? Does that matter?

Did shakeout bags give maximum performance?

Did the US reduced motor-speed affect efficiency?

Sadly, the Kirby Classic is too difficult for me to find here in the UK. I'd like to own one. My demo will be an unmodified Tradition v Modified Tradition v Legend II. It's going to be a few weeks before I can run my own side-by-side tests.

As an aside - I've heard that Shake'n'Vac, dried Shampoo, etc. were culprits for many rotten tubes.

How does the upgraded tube compare with the shakeout bag? I've been contemplating reverting to shakeout.

Thank-you everyone for your input thus far. I'll revisit this in a few weeks and let you all know my findings when all three machines are up-and-running.

(I think I'd forgive my Tradition no matter what. She looks gorgeous).

Post# 393517 , Reply# 8   6/19/2018 at 10:50 by tommymilan (milano)        

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To me a Tradition or an Heritage with shakeout bags have tremendous airflow, are more powerful than with even the best bags. As long as you're not concerned with filtration. Any Kirby with proper bag filling system and proper high filtration bag actually clean better for the simple reason that they don't blow clouds of fine dust all around your home and I must say that I prefer slightly less suction/airflow in favour of better filtration. No matter how much I love any beautiful vintage vacuum cleaner in itself, and maybe run them a little bit for fun, not for cleaning my house. And believe me, I'm not a total clean freak. Just like things to be done properly.

Post# 393653 , Reply# 9   6/21/2018 at 13:32 by sptyks (Skowhegan, Maine)        

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I believe the shakeout bags provide the most airflow allowing for better cleaning performance.


Where did you hear that Kirby motors run slower in the U.S.? As far as I know all Kirby motors run at the same RPM weather it's connected to 120 or 240 volts. It all has to do with the Armature and Field windings

Post# 393655 , Reply# 10   6/21/2018 at 14:15 by KirbyClassicIII (Milwaukie, Oregon)        

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As far as I know, the 240-volt export Kirby motors were single speed but used the high speed wires (red and white together). It was not until the Heritage that the Kirbys sold outside of North America would have motors with two proper speeds like our 120-volt examples.

James Sandilands' 1979 Kirby Tradition 3CB:

And one of ours...


Post# 393702 , Reply# 11   6/22/2018 at 12:17 by sptyks (Skowhegan, Maine)        

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To Ben and Alan:


I have read here on Vacuumland, in other threads, that running Kirby motors for long periods of time at high speed can damage the motor. Is this true or not?





Post# 393712 , Reply# 12   6/22/2018 at 16:22 by KirbyClassicIII (Milwaukie, Oregon)        

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As far as I know, no. Not that I would try to, anyway.

All I've seen was that running the motor while using the inflator/deflator tool with the hose may damage the plastic fan (as used on later Traditions and up to the G4) after about five minutes of constant use.


Post# 393713 , Reply# 13   6/22/2018 at 16:33 by rugsucker (Elizabethton TN)        
"high speed can damage the motor"?

In most cases when a Heritage was brought in for repair with bad carbon brushes I would hear the same thing-- 'We took up all our carpet and only use it with the hose(high)'.Most would run like new after changing carbons.

Post# 393770 , Reply# 14   6/24/2018 at 12:51 by Rowdy141 (United Kingdom)        

Stan: I can't see high-speed itself being a problem for the motor. It's not as though you're over-revving it in any way. The motor was designed to run at high speed - for hoses in the US, and constantly in the UK. Think of the speeds as Slow/Normal, rather than Normal/High.
I guess the issue would be airflow cooling the motor. If it's starved of air (say with a Crevice-tool) for prolonged periods, that would warm the motor, but damage it?

There are owners who abuse vacs. Perhaps this cautionary warning stems from owners who were vacuuming brick-dust or soot, for hours on end, instead of using a Commercial/Industrial machine?

Post# 393772 , Reply# 15   6/24/2018 at 13:08 by Rowdy141 (United Kingdom)        

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