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 Post subject: Carburetor in pieces!
PostPosted: Sun Jun 02, 2013 7:16 pm 
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Location: Lewes, East Sussex - UK
I cleaned the outside of my carb with brake and parts cleaner and it seemed to work quite well. So that prompted me to take the Carb right off and dismantle it - How many jets has this thing got!! I have added pictures at the bottom as they don't quite match each part of my queries, but are related.

I found a couple of things which I don't think are quite right. Obviously, I haven't managed to order the bits which do not come in the gasket kit which I obtained from Haflinger technik. The accelerator pump I take to be the seal with a big spring on it and a system like a bicycle pump. The seal on that has a slightly damaged edge so maybe it is not doing quite what it was designed to do.

The other strange one is the jet just above the external throttle lever. It has a ball bearing in it and a "ding" in the end of the tube to stop the ball bearing from falling out. What on earth does that do? The pressure of fuel seems to be going the wrong way for the ball to act a stop and if it is going the other way, then it will never seal and that makes it pointless. Part number for this?

Then there it the jet at the bottom of the accelerator pump cylinder. Is this supposed to have a little bakerlite flat washer in between the two bits of jet? I presume that would make it a flap valve - What is the part number for that item and where can I get one? I have made a temporary one as there were the remains of some thing which looked like the item I described above. Because of the remains, I have put a flat washer in there made from a gasket material I had lying around.

Carb before cleaning:-

Attachment:
Haflinger carb.jpg
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Carb top after cleaning:-

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cleaned carb top.jpg
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My choke plate does not look like the images in the books:-

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choke 1.jpg
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That took some working out to get it back together in what I hope is the correct orientation. I forgot to take pictures of it before I took it apart! (basically, grubby hands and cameras don't go together very well).

And finally, all back together again:-

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back together and running1.jpg
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back together and running2.jpg
back together and running2.jpg [ 112.16 KiB | Viewed 2631 times ]


Took most of the day taking it apart and putting bits in a small ultrasonic cleaner (if they fitted) and then re-assembling and trying not to make a mistake!

It will probably have to come apart again when I get the accelerator pump and things. It runs better than it did before I took the Carb apart, but I still won't say it is as good as it is going to get.

John

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PostPosted: Mon Jun 03, 2013 1:09 am 
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Hi John,

...the jet just above the external throttle lever. It has a ball bearing in it and a "ding" in the end of the tube to stop the ball bearing from falling out

This is the Suction Valve which is part number 700.1.08.447.2. When you remove this from the carb you must replace the Seal Ring which is part number 700.1.08.452.1. The seal ring is aluminum with dimensions of 12x9x1mm.

...the jet at the bottom of the accelerator pump cylinder. Is this supposed to have a little bakerlite flat washer in between the two bits of jet

This is the pressure valve which is part number 700.1.08.415.0. The bakelite portion you refer to should be a soft pliable seal. This is the reason that the pressure valve always fails. The rubber seal often disintegrates or turns hard like yours has and no longer forms a seal against the bottom of the accelerator pump's piston when the throttle is opened. The purpose of this is to lean the air/fuel ratio at higher RPM's. Note that this little rubber seal is not available as a separate part so you must buy the complete pressure valve assembly.

Like the Suction Valve, when you remove this from the carb you must replace the Seal Ring which is part number 700.1.08.453.1. The seal ring is aluminum with dimensions of 11x8x0.8mm. In the center of the Pressure Valve is a small screw (jet) which can be removed but I don't recommend doing so as they are very difficult to reseat and will leak fuel mercilessly once disturbed.

For both the Suction Valve and Pressure Valve watch carefully once you've reinstalled the carb on your Haffy. Both are prone to leaking fuel and can quickly turn your truck into an inferno on the side of the road.

The accelerator pump I take to be the seal with a big spring on it and a system like a bicycle pump. The seal on that has a slightly damaged edge

Yes, this is the Accelerator Pump Piston and is part number 700.1.08.411.0. The original piston used a leather seal which hardens with age and its edge deteriorates. The new replacement pistons use a Viton seal which should last much longer provided that the petrol is not permitted to go stale in the carb. The shaft length of the piston for the NDIX on Haflingers is shorter than those found in Pinzgaurers and Unimogs.

The last time I checked Haflinger Technik only had the Accelerator Pump piston available. All of the parts I mentioned above are available from Expedition Imports, Robert Prokschi and Autoquariat.

There are some very good online articles on rebuilding and tuning the Zenith NDIX. One of these articles is on Expedition Imports website and another written by Ron LaDow is at http://porsche356registry.org/resources/tech-articles/troubleshooting-and-repair/480-rebuilding-zenith-32-ndix-carburetors.html

Cheers,
Steve


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700_1_08_411_0 Accelerator Pump-1.jpg
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700_1_08_415_0 Pressure Valve-1.jpg
700_1_08_415_0 Pressure Valve-1.jpg [ 41.49 KiB | Viewed 2613 times ]
700_1_08_447_ 2 Suction Valve-1.jpg
700_1_08_447_ 2 Suction Valve-1.jpg [ 13.02 KiB | Viewed 2613 times ]
01_40_00.JPG
01_40_00.JPG [ 39.08 KiB | Viewed 2613 times ]
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PostPosted: Mon Jun 03, 2013 5:51 pm 
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Many thanks for the links Steve.

Still doesn't help trying to find out what the little bakerlite flap valve washer thing is as it is fitted in between two brass "jets" (Item 103) in the above picture - on my Carb is actually two bits. One screws into the other from the bottom and there is (was) the little bakerlite washer - must be 3 mm in diameter.

When I place my order for the 3 items you have list above and receive them. I shall have to take the Carb apart again in order to fit them, so I will take photos of the replacement washer I have put in.

On another point about tuning the carb - my idle mixture jets (Item 26) have to be screwed ALL the way in to achieve a smooth tick over. They don't appear to be "notched" but obviously you can tell they have "hit bottom" as there is a shiny ring on them. If you start the tuning with them 1.5 turns out, the exhaust can be seen to be putting out "black" smoke (i.e. rich) and as you turn them in the black smoke disappears - which doesn't make sense to me as surely if you are cutting off air, the mixture should be getting richer not leaner?

Must admit I don't understand why they are in the governor choke block and not in the Carb body proper. But then it wasn't me who designed the Carb!

John

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PostPosted: Mon Jun 03, 2013 6:34 pm 
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Hi John,

Quote:
Still doesn't help trying to find out what the little bakerlite flap valve washer thing is


As I expalined in my last message this is NOt a "bakerlite" flap valve. It is a rubber o-ring seal that seats against the bottom of the accelerator pump piston when the throttle is substantially (dependant on linkage adjustment) opened. Your part only appears to be hard like "bakerlite" because it is dried out rubber. It should be soft and pliable as you will see when you receive your new pressure valve. If this seal is not working properly your engine will noticeably lack acceleration and top-end power as the engine will be running on a very rich air/fuel ratio due to excess fuel flow in the high speed carb circuit. Look closely at the left side of the photo I posted above and you will see the protruding edge of this seal in the face of the Pressure Valve.
Yes, this valve includes a second portion in the center which can be unscrewed but per my warning in my last message don't disturb this center screw. There is no point in doing so anyway as the parts are not available as seperate components and you risk a severe petrol leak and fire.

Quote:
On another point about tuning the carb - my idle mixture jets (Item 26) have to be screwed ALL the way in to achieve a smooth tick over. They don't appear to be "notched" but obviously you can tell they have "hit bottom" as there is a shiny ring on them. If you start the tuning with them 1.5 turns out, the exhaust can be seen to be putting out "black" smoke (i.e. rich) and as you turn them in the black smoke disappears - which doesn't make sense to me as surely if you are cutting off air, the mixture should be getting richer not leaner?


Your logic is inverted when you describe the mixture screw operation in your post. When you turn the screws in you are reducing fuel flow in the carb circuit and NOT "cutting off air".

Quote:
Must admit I don't understand why they are in the governor choke block and not in the Carb body proper. But then it wasn't me who designed the Carb


The adjustment screw are in the throttle plate of the carb and NOT the governor choke block. The governor choke block is integral to the intake manifold casting.

Hope this clears things up for you.

Cheers,
Steve


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PostPosted: Mon Jun 03, 2013 8:22 pm 
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Hi Steve,

Many thanks for clearing some things up. In fact I now believe that the pressure valve you talk of as being made up of two parts and that you shouldn't take them apart, is actually the bit I DID take apart, (there not being any warnings in the manual or anywhere other than this thread) not to do so!

Having taken it apart, I found there is 3mm diameter bakerlite flap valve washer in there and that mine had obviously been damaged by some who had dismantled and replaced it previously as it was in two pieces. I manufactured a replacement and have put it back together again.

It is of course possible that this little washer is something that has been added in the past by someone for some reason. Not that it really makes any difference in the long term as I am going to by a replacement, but it might in the short term whilst I wait for the bits to arrive.

Now that I know this part can leak if disturbed, I will make sure to check it for leaks before using Lurch.

I shall try to order all the items for which you have listed part numbers as they were not items which were included in the Carb kit I received. That appears to be as suggested in the link you sent, a generic Carb gasket set. There were items in it which did not seem to go anywhere on my Carb.

The link to the Porche version of the Carb just shows up that there are variations of the same basic casting! Their one does not have the choke lever like ours.

As you say, I have things round the wrong way regarding the idle mixture screws, but it still means there is something wrong with the Carb. If the screws have to be all the way in to "lean" out the mixture then that must mean there is too much fuel coming down that particular set of holes. The jets relating to that circuit at the top of the float chamber are 40's as per the book, so through which jet does the fuel go through?

John

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PostPosted: Mon Jun 03, 2013 8:57 pm 
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Hi John,

Quote:
If the screws have to be all the way in to "lean" out the mixture then that must mean there is too much fuel coming down that particular set of holes. The jets relating to that circuit at the top of the float chamber are 40's as per the book, so through which jet does the fuel go through


The cause of the rich condition isn't that too much fuel is passing through the main jets (the section that is affected by the adjustment screws). By closing the screws you are compensating for another problem. Your carb's problem is that the seal ring on the Pressure Valve are not functioning properly and fuel is freely passing through the valve from the pump chamber through the #40 Pump Jets that you've mentioned thus feeding unmetered fuel to the cylinders.

Once you have replaced your Pressure Valve, Suction Valve and Accelerator Pump Piston you will need to follow the procedure in Ron LaDow's article to adjust the Accelerator Pump linkage as well as the adjustment of the mixture screws. The pump linkage adjustment is critical and has a very dramatic affect on engine performance and fuel consumption rate.

The Zenith NDIX is a curios design of three independent carburetors in a single body casting. The body contains the Start (Choke) circuit which is actually a carb with enriched jetting that is engaged by the external lever which also bypasses the left and right Main carb circuits. While the Porsche 356 version of the Zenith 32 NDIX carb does not include the Start (choke) circuit all other details in the repair article are directly applicable.

Cheers,
Steve


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PostPosted: Tue Jun 18, 2013 5:53 pm 
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I have now received some bits from Robert Prokschi but unfortunately it looks like he no longer has the jet with the "O" fitted to the end as I have received just a tiny "O" ring - presumably to replace the one on the end on my existing jet. As I am not 100% sure if there should be a little flap valve washer in between the two bits of that jet, I had hoped to get a complete new one to replace it with. Not going to happen now it seems.
So now Lurch waits for the day I have enough time to dismantle the Carb again to put the new bits in.

John

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PostPosted: Fri Nov 20, 2015 1:52 am 
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The events in this thread happened a few years ago, but perhaps you remember:
How did you eventually solve the problem with the mixture screws having to be turned all the way in?
And what ended up happening with the pressure valve and the tiny o-ring?

I'm dealing with this exact same thing right now. At least I think so.
I can't figure out where the tiny o-ring goes or what Steve means about it sealing against the pump piston. I dont see how the pressure valve can possibly seal against the pump piston. There's a slot in the pressure valve face! I must be understanding this wrong.
And to tune the carb using the manual instructions, I end up with my mixture screws all the way in.


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PostPosted: Fri Nov 20, 2015 2:29 am 
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Yakov wrote:
And to tune the carb using the manual instructions, I end up with my mixture screws all the way in.


I cannot answer the other aspects of your question but if your mixture screws end up being all the way in, I can only state the obvious and say you have other issues. I remove both screws and clean with carby cleaner (do not damage) and squirt cleaner in both holes and reinsert the screws.

I then follow the instructions on page 38 of the owners handbook. Screw both screws in all the way by hand (do not force) then open 1/2 a turn. Have engine warm and throttle cable set so engine idles around 700-800rpm. Adjust each screw in turn, in or out until max revs are achieved. For my engine this is wind out another 3/4 of a turn - so out 1 1/4 turns from right in.

Then adjust throttle cable idle adjuster so idle drops back to 700rpm (I find this a bit low so I set mine to about 900rpm).

This has always worked for me so I can only state the obvious that if yours have to be all the way in there are other issues in your carb.

Do you know what jet sizes are in your carb - those in the know may be able to tell you if there is an issue with the sizes.

Good Luck

Garry

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PostPosted: Fri Nov 20, 2015 4:12 am 
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Just replace the accelerator pump and valve(part with disc) with updated Unimog or Pinzgauer pump valve. this combo works well.
I build a lot of these Zenith carbs for Mogs/Haflingers and Pinzgauers, the old valves eventually leak fuel.
If it runs with mixture screws in, either float level is too high or needle bores in throttle body are damaged or worn.
Idle speed is 700rpm per service manual.

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PostPosted: Mon Nov 23, 2015 3:36 am 
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I did replace them with Mog parts. Nothing I tried leaned out the mixture without turning the mixture screws all the way in. I have all stock jets, and I tried larger pilot air correction jets. No change.
Replaced mog pump piston with a porsche one that had a better skirt, no luck.
Lowered float level, raised float level, nothing.
Adjusted accelerator pump closing point according to the manual, nope.
Cleaned the mixture screw holes and bypass holes with carb cleaner. Cleaned pump valves.

It runs okay, doesn't always transfer well, but entirely driveable, just too rich and setting the idle according to the manual only results in the screws all the way in.

I guess it could be worn bores in the throttle body, but I really hope there's another explanation... :(


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PostPosted: Mon Dec 07, 2015 3:36 am 
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Having run out of things to adjust, replace, and try, I put in the worn out mixture screws from when I first rebuilt the carb. These had been so abused before me that they did not merely have grooves, but needle had so much material missing it almost looked like a different design, as the taper didn't start at the same diameter as the threading, but seemed stepped down somewhat.
Anyway, these completely worn out-looking mixture screws did the trick. They screwed in much further than the brand new ones and allowed me to tune the carb properly for the first time ever. All the way in stalled the engine, which the brand new screws could never do.

I suppose that my choke block really is worn from whatever idiot screwed them in so tight. I'm just glad it still works okay with the old screws.


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PostPosted: Mon Dec 07, 2015 8:59 am 
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Were the new screws genuine or aftermarket? I have three makes of classic vehicles and have to use repro parts and I would say that many of them are not worth the money I pay for them, wrong size, wrong material, poor fit etc etc - though not always possible use OEM if you can.

Maybe this is the situation you have found.

Glad it is sort of sorted.

Garry

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