Ducati 900 Supersport 1989 is going back to Weber

[slepsnys]

Hello to everyone,
I am a new owner of Ducati 900 Supersport 1989. This is my first Ducati. I have read this forum a lot before buying this motorcycle, but now I can't find answers to my questions, that's why I have created new post.
This is my motorcycle:

It came with Dellorto carbs PHM40 and I want to covert back to Weber 44 DCNF. So I have bought Weber "44 DCNF-118 9J" from Germany it came with airbox and intake manifolds:


When I have attached these manifold to the engine and tried to fit Weber manifold, it looked not straight, but turned to right side:


I want to ask if it is normal when fitting Weber or the manifolds that came with Weber carb are not original and from another bike and angles are wrong?

[paso750]

Hi, the links to your pictures don`t work but did you try to swap the carb manifolds? They are not identical (according to the part numbers).

[slepsnys]

I have updated links, so now they should work. I have tried to swap manifolds and result is same, so both manifolds are identical.

[paso750]

install the rubber boots. They have an impact on the carbs position. (and eventually try to swap the manifolds again;)

[slepsnys]

So, to answer my question, these manifolds are right for Weber carb?

[paso750]

Yes those are Weber manifolds.

It`s interesting looking at the parts catalogues (unfortunately we don`t have one for the 900SS). The vertical and horizontal carb manifold have the same part numbers on the P750 and the 750S (037098780). On the 750S tho there exist two types, hence two part numbers (037098780 & 037098783). The 906 uses the 037098783 for the horizontal cylinder and a 13710021A for the vertical one. 13710021A is the manifold that the 907ie uses on both cylinders.
Maybe the manifolds for the 900 engine are the same on both cylinders and just one part number was superseded.

[Mc tool]

I seem to recall having a similar issue with my 906

[slepsnys]

To: Mc tool
And what You have done to resolve this issue? Fitted other manifolds which where straight or adjusted this issue it with rubber boots?

[Mc tool]

Twas a while ago now but Im pretty sure that the two intake manifolds are different ,but not by much so it aint immediately obvious .Being Ducati , its a bit half arsed and the carb more than likely wont line up perfectly flat and square , which is probly why its hidden under the tank If you put the whole lot together and leave the hose clamps loose it may be possible to improve things by rotating the rubber sleeves , or even swapping them around . Sometimes the rubber deforms over time and if you pull em to bits they have to go together exactly ( the same rubber the same way up on the same manifold and oriented the same way ) the way they came apart or they will look wonky

[MarkST]

Hi slepsnys and welcome to the forum.

That's a nice looking bike you have there, but why do you want to put it back to the single Weber ?

[slepsnys]

Thank You.

I want to put Weber back because I want bike to be in original condition as possible with its unique automotive carburateur.
To begin with when I got the bike Dellorto PHM40 NS ans PHM40 ND has issues, they where flooding the engine, leaking. I have looked in to these carbs and noticed that according to Dellorto book they where suited for two stroke engine, because of atomizers surround shape (oval is cut).

So I have decided to go back to Weber. I have read Higgy and Romus post about Weber and their posts convinced me that 900cc Ducati engine can work good on Weber with 4.5 aux venturi and apropriate jetting.

[MarkST]

Ok thanks for the explanation. I understand now.

[deswoodau]

Hi Slepsyns,

I also persisted with the dcnf 44 on my 750 Sport and fitted 4.5 aux venturis with larger jets which helped improve the bike on lower end performance. I'm much happier with the riding experience and nothing quite beats the sound of a weber Ducati! It really does sound incredible. Good choice reverting to original.

As for your problem, the manifolds and carb do need a little bit of care moving into position once the rubber boots are on.

All the best.

[slepsnys]

Today I have received 4.5 aux venturi for Weber. Weber number is 71107 or 71107450, because they are 4.5 in catalog they where marked as DCNF40, not DCNF44. They are different finish than original, it is very rough and without 4.5 marking, so I have polished one venturi, this is a comparison photos. On left is polished and on right isn't.


This 4.5 venturi is different inside than original 3.5, it has thicker walls.

Original 3.5 venturi:

New 4.5 venturi top:

New 4.5 venturi bottom:

So my question would be if I have bought the appropriate 4.5 venturi for DCNF44?

[deswoodau]

They look the same as what I installed recently.

I didn't polish mine either and it performs fine.