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My 24 Roadster was giving me trouble starting and I thought it was due to remaining crud in the fuel system getting into the carburetor. It would still run reasonably well, but was giving me dificulty starting it unless I primed the cylinders. Since I haven't solved the starter issues yet, this is all hand cranking.  I've gone from starting first crank every time to great difficulty.


Tonight I took it apart to clean it out. A little stuff was in it, not much, maybe enough to cause problems. But when I got everything back together I looked down and there was one bb sized ball left. I didn't see it come out and have no idea where it came from. I do think it came from the carburetor, though, because I cleaned the table before starting and spread new paper towels across everthing. So, my question now is, where the heck does it go.


I've found this drawing on another thread on this forum, and I find no ball bearing/BB in it.  I didn't disassemble the lower part with the "choke" gears, etc, and didn't remove the big brass slide valve from the center part. 


Anyone know where it might go? (The drawing says 27 Carburetor, but it appears to be the same)


Also, I'm not familiar with the adjustable thing on the intake, which spins around and either lets air in from the engine compartment around the carburetor, or when closed, from the inside of the engine. Can I assume this is a cold weather setting? Engine compartment air when warm outside, from inside when cold? Or is something else going on?


Thanks for any help.



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There are two ball check valves in the base of the air valve that act as a damper control on the air valve , this is to allow extra fuel ( like a accelerating pump ) when the throttle is opened suddenly.The valves can only be removed if the air valve is taken apart, the balls are held in by brass pins.

Edited by robert b (see edit history)
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Rarely, but it does occur, wear will cause the pin to break, and a ball to fall out. I would suggest inspecting the dashpot.


Removing the dashpot is generally difficult, as a special tool is required. Look at the picture of the bottom of the dashpot supplied by Robert. Note there are 5 holes:


(1) in the center for the metering pin

(2) opposite each other with the check balls

(2) "dummy" holes opposite each other and at 90 degrees to the (2) with the check balls.


The "dummy" holes are used to remove the dashpot.


The special tool may be fabricated by machining a round piece of steel that is roughly 1/4 inch thick, and a diameter approximately 0.015 LESS than the diameter of the dashpot cylinder (the cylinder containing the dashpot). Now machine three holes in the top of the round piece of steel to insert pins that will fit into the two dummy holes and the metering pin hole. Now weld a handle onto the bottom of the round piece of steel.


Once the tool is fabricated, it can be placed in a vice to support the dashpot, and the top portion of the dashpot (the aspirator valve) unscrewed. The dashpot may now be repaired.


Before final reassembly of the dashpot and aspirator valve into the carburetor body, it is a good idea to gently "lap" the sealing area of the aspirator valve into its seat with valve-lapping compound. WASH THE AREA COMPLETELY AFTER LAPPING.


(opinion) the Stewart (made by Detroit Lubricator) was one of the top three (Stromberg and Zenith the other two) carbs of this period. But even the best sometimes requires a wee bit of maintenance after 90 years.



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RobertB, the air valve on your Stewart carburetor is different from mine. Mine is mushroom-shaped and has no holes like yours has. Maybe they used different air valves Down Under than they did in the States?


The Stewart carb may have been OK for its time, but it is very primitive in a number of respects. (Remember, it dates back to 1913 or before.) It has relatively poor mixture control and throttle response. When you think about it, its method of operation (the way it lifts the air valve) really conflicts with Bernoulli's principle!


The fact is, just about the only reason auto manufacturers used updraft and sidedraft carbs back then was because downdraft carbs were considered unsafe. But the Stewart carb is reliable because it is so simple that almost nothing can go wrong with it.

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Are you sure the choke cable hasn't slipped?

The "choke" isn't actually a choke but rather lifts the needle to flood the carburetor for starting.

The return spring needs to be fairly strong in order to take and keep the lever off of the needle or the engine will run rich.

The knurled needle is an air adjustment and operates opposite of most other other carburetor adjustments so you have to think backward when making the setting.

Turning the needle IN increases the fuel.


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Best I can tell, the balls are both where they should be. "Choke" hasn't slipped. I really think I just had a couple flakes of gunk in it. The extra ball, which all indications are it is, threw me off. It ran quite well so I don't think the ball had come from there, it was just junk left from some previous guy. I hope! Got side tracked making an old flathead ford fire truck run so we can sell it, now hopefully I can put the carburetor back on tomorrow and see how it does.


I got new generator/starter brushes from Myers today, I'll put them, maybe tomorrow too, in but Ihave slim hopes that will solve the starting/charging problem.

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  • 1 month later...

To follow up on this, I did reassemble without the extra bb sized ball. Both of the ones mentioned above seemed to be where they should.

I've since driven it several hundred miles and it's worked just fine. My conclusion is I had extraneous junk in there from some previous tinkerer.

I've hauled it to our other home in south Texas and am using it like a daily driver. Causing quite a bit of talk around here!

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