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 Post subject: Wanted: pictures of your Weber carb
PostPosted: Wed Nov 21, 2018 3:19 pm 
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paso grand pooh-bah
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Location: southern Germany
model: 750 Paso
year: 1987
There are the following:

P750 - 44DCNF 107
P750 - 44DCNF 110 (US)
P906 - 44DCNF 113
750S - 44DCNF 116 (according to some Ducati books it's a 113 so maybe like on the Paso there were different versions depending on target country)
900SS - 44DCNF 118 (-"-)

The question came up recently (again) what the differences are. I personally doubt it's just the jetting. Instead I think the difference could be the number and size of the progression holes. To see the progression holes you'll have to turn the Weber upside down and open the throttle valve. The pictures below show a 44DCNF 110. It would be great if you have one of the other models and could post a picture for comparison. I will post this in three forums although I don't like double posts. When I get some replys all info will be joined into one topic and the other two will be deleted.

thanks,

G.


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Thu Dec 27, 2018 1:04 pm 
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model: 750 Paso
year: 1989
Hi Gerhard,

I will send a picture of my 44 dcnf 107 progression holes the first occasion I have it disassembled.
But I have also a 44 dcnf 112 (7M) version (= 750 USA version) I obtained it as a spare one for easy/quick exchange during tuning activities (later on in the process).

Just to let you know there seems to be also a "112" version.

If you want me to pass other info just let me know (e.g. jets etc.).

Regards,

Frank

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Thu Dec 27, 2018 1:36 pm 
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model: 750 Paso
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Gerhard,

Here the progression holes pic from the 44 dcnf 112.
This one has 5 holes.

Ciao,

Frank


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File comment: Weber 44 DCNF 112 7M - progression holes
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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Tue Jan 08, 2019 6:31 pm 
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paso grand pooh-bah
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Frank, thank you so much for the picture!!! :thumbup: I'm now guessing the 107 only has 3 progression holes.
As posted a long time ago

Quote:
My Weber/Dell orto (DCOE, DCO/SP & DHLA) book says "Both manufacturers have made emission versions of their respective carburettors, but these are not as good as the 'universal performance' versions, in terms of best possible all around accelerative and top end performance. Note that one of the quickest ways to establish at a glance wether a sidedraught Weber or Dellorto carburettor is suitable for high performance use is to count the number of progression holes. Any carburettor which has two or three very small diameter (1mm, 0.040inch) progression holes will have a rich progression phase, all other factors being equal. Carburettors with five quite large diameter (2mm/ 0.080inch) progression holes will have a weaker progression phase, all other factors being equal."

Maybe the 110 was on the standard US P750s and the 112 on the California models.
Now I'm really curious about the 113, 116 and 118...

G.

PS: Is that next to the point of the adjuster screw a crack?


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Tue Jan 08, 2019 7:01 pm 
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Hi Gerhard,

Best wishes, just looked at my 44 DCNF 107 and it has 4 progression holes :dunno: .
As soon as it of the Paso I'll send you a picture.

Regards,

Frank

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Tue Jan 08, 2019 7:05 pm 
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paso grand pooh-bah
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Interesting. Then they are probably smaller than the ones in the 110.


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Wed Jan 09, 2019 8:44 am 
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Yeh,, it's a small crack, previous owner will have over torqued the adjuster screws.
Not a big deal, just for synchronizing.

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Wed Jan 09, 2019 9:00 am 
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Sorry, slip of the tongue: idle mixture .... :oops:

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Wed Jan 09, 2019 9:57 am 
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Gerhard,

I will try to measure the holes in the near future (will use the rear of small calibrated drill bits).
By the eye the lowest one is always smaller than the rest.
But I will check it for the 107 & 112.

Frank

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Wed Jan 09, 2019 11:14 pm 
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Whats the diff ?
Is it the actual number of holes , the combined area of the holes or the length of the series of holes ( like how far the throttle plate is open before the last hole is completely uncovered. Maybe you could convert a 3 hole or 4 hole into a 5 hole by "lengthening " the last hole ..............just thinkin :evil: :P

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Sun Jan 13, 2019 4:02 pm 
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paso grand pooh-bah
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Mc tool wrote:
Whats the diff ?
Is it the actual number of holes , the combined area of the holes or the length of the series of holes ( like how far the throttle plate is open before the last hole is completely uncovered. Maybe you could convert a 3 hole or 4 hole into a 5 hole by "lengthening " the last hole ..............just thinkin

Good question. From my understanding (and someone please correct me if this is incorrect) it's all three and yes ;) The position (distance from the closed butterfly valve) and number of the holes define how wide the progression phase is while the number and size of the holes will determine how strong the effect of the progression circuit is. The small hole is the first to be uncovered when the butterfly opens. I wonder if that is to slowly start the progression phase or because a small hole will react stronger or quicker on the flow passing by.

taken from: http://240260280.com/Tech/Carbs/Weber/D ... uning.html
Quote:
The DCOE Progression Circuit (for slow transitions from Idle Circuit to Main Circuit):
As the throttle valve slowly opens, when transitioning from the Idle Circuit to the Main Circuit, the air flow required to activate the main circuit does not occur quick enough. This delay in the main circuit starting causes a lean spot between Idle and Main. The solution is to simply add more fuel holes near the throttle valve. These holes are drilled upstream of the idle needle valve port. As the throttle valve is opened, it exposes each successive hole to the manifold vacuum and air flow. In turn, (due to high velocity air and manifold vacuum) it draws more mixed air/fuel from each progression hole.

What I do not understand is that in the quote some posts up it says:
Quote:
Any carburettor which has two or three very small diameter (1mm, 0.040inch) progression holes will have a rich progression phase, all other factors being equal. Carburettors with five quite large diameter (2mm/ 0.080inch) progression holes will have a weaker progression phase, all other factors being equal.

The progression circuit is directly connected to the idle circuit so there's air/fuel mixture coming through those holes. How can less and smaller holes make a rich progression phase?
Where are our carb specialists? :truck:


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Sun Jan 13, 2019 5:56 pm 
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paso grand pooh-bah
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Quote:
How can less and smaller holes make a rich progression phase?


Smaller and fewer holes will concentrate the vacuum over a narrower range of throttle opening

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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Sun Jan 13, 2019 6:16 pm 
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paso grand pooh-bah
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I agree that the progression phase will be narrower but why would it be richer?


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Sun Jan 13, 2019 9:01 pm 
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paso grand pooh-bah
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Stronger signal will pull more fuel. Higher pressure in the float chamber pushes more fuel into the low pressure of the venturi if that makes more sense

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There's no problem so bad that a little fixing can't make it worse! : )
If it ain't broke keep fixin it till it is
88 750
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92 907ie


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 Post subject: Re: Wanted: pictures of your Weber carb
PostPosted: Mon Jan 14, 2019 9:43 am 
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Gerhard,

I had the same question, to be honest I would rather assume the other way around ... ( more holes = more surface = less resistance = more fuel mixture from the idle circuit).

Just saying: I want to believe the remark but I don't understand it (I'm not a Weber specialist just an interested bystander).

Frank

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Suzuki SV1000S - 2008
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