NGC - Down draft Weber Carbs

[SIR REAL ED]

any one have any experience with dual throated down draft weber carbs?

If so, lets hear about it!

Thanks in advance.

[Bisbee]

 I rebuilt my dual 40mm side draft webers for my Alfa Duetto years ago.  Any problems?

[mondtster]

Is there some specific information you're looking for? I've worked on a number of them, they're just like any other carburetor in my book. There is some decent documentation floating around on the internet about them if you search a bit.

[FarmallA]

It's been years since I've dealt with Webers. There are two types of 2 barrel downdrafts (or maybe more?).  IDF's have 2 equal size chokes that are linked together.  The DGV type has two different sizes of chokes that open progressively, the small one first.

Not knowing your application, my guess is you're looking at a DGV.  Great on a 2002, MGB, etc.  Once they are jetted properly, they are very dependable. Like all carbs, ethanol can screw 'em up. 

There are different types of enriching (butterflies) systems.  Water, electric manual.  I think the electric was called DGEV.  32/36 is a typical choke size.

i always preferred SU's on my Triumphs.  But the the Weber was better than the Solex on a BMW. 

Weber sidedrafts are great too (DCOE), but really need a cam to be worth it.

That's all I know.

FarmallA
Steve

[SIR REAL ED]

I have a wild hair idea of possibly replacing the downdraft Mikuni carbs on my TDM850 with a single dual throat carb setup.  I remembered the old kits for some inline fours in the 1970's, that, IIRC consisted of a pair of dual throated side draft Weber carbs.

So I am curious in terms of dimensions, availability, ease of tuning, etc.  All the associated information one would need to make an informed decision to either take a leap and try installing a single dual throat carb (assuming I am using the right terminology) or realize it is a foolish idea.

I said Weber carbs, simply because that is the name I am familiar with.  I am also interest in any equivalents.

thanks in advance.

[FarmallA]

This site came up right away, have some maybe useful info:

https://www.pegasusautoracing.com/document.asp?DocID=TECH00151

Didn't the Ducati Paso have a downdraft Weber?  Yes, a 44 DCNF.

Here's a thread about messing with the Paso Weber.

http://forums.ducatipaso.org/viewtopic.php?t=747

 This guy replaced it with a 40 DCNF and had better results he says.  That's for a Paso 750, Your TDM is an 850, so who knows?

Making an intake manifold to fit should be fun.

But Mikuni carbs are supposed to be good too.  Worked great on my old 750 carby Monster once I returned it all to stock from the abomination it was when I first got it. (painfully loud and it ran like crap).

FarmallA
Steve

[nc43bsa]

It's interesting that you want to replace Mikunis with a dual-throat Weber when in the 90s everyone with a Ducati Paso was replacing the dual-throat Weber with Mikunis.

I found that the problems with Pasos with Webers were solved once you had the parts and experience to properly tune the Webers, which came from Ducati horribly jetted for the SE US.

[Turin]

I had a 750 Paso and the weber worked fine after you played with the emulsion tube and added a fuel pressure regulator. The Paso forum details are dead nuts on. That said, mikuni makes fine carburetors and I'm fitting a set of Mikuni HSR's on my ongoing project.

[SIR REAL ED]

This site came up right away, have some maybe useful info:

https://www.pegasusautoracing.com/document.asp?DocID=TECH00151

Didn't the Ducati Paso have a downdraft Weber?  Yes, a 44 DCNF.

Here's a thread about messing with the Paso Weber.

http://forums.ducatipaso.org/viewtopic.php?t=747

 This guy replaced it with a 40 DCNF and had better results he says.  That's for a Paso 750, Your TDM is an 850, so who knows?

Making an intake manifold to fit should be fun.

But Mikuni carbs are supposed to be good too.  Worked great on my old 750 carby Monster once I returned it all to stock from the abomination it was when I first got it. (painfully loud and it ran like crap).

FarmallA
Steve

I found that first website last night after reading the replies you guys posted.  I suspect they will be able to provide enough information to make an intelligent (?) decision as to whether the attempt will be worth the time, effort, and money.

Many thanks for the link to the second website.  I suspect that will have some very valuable information.

44mm carbs on a 750 tuned for torque?  Easy to believe the 40mm carb was a much better choice.

[SIR REAL ED]

It's interesting that you want to replace Mikunis with a dual-throat Weber when in the 90s everyone with a Ducati Paso was replacing the dual-throat Weber with Mikunis.

I found that the problems with Pasos with Webers were solved once you had the parts and experience to properly tune the Webers, which came from Ducati horribly jetted for the SE US.

Right now it is just a wild hair idea based on possibly having more room in the space envelope.  Space envelope and Weber dimensions will determine viability.  I've never seen a design problem yet where the space envelope was not a major issue.

It could be a stupid wild hair idea, I've had those type of attacks in the past....

Stock carbs are working great by the way.

[SIR REAL ED]

I had a 750 Paso and the weber worked fine after you played with the emulsion tube and added a fuel pressure regulator. The Paso forum details are dead nuts on. That said, mikuni makes fine carburetors and I'm fitting a set of Mikuni HSR's on my ongoing project.

what is the ongoing project getting the Mikuni HSR carbs?

Enquiring minds want to know!

[SIR REAL ED]

Thanks to everyone who has contributed to this thread.

While this is a low priority, tinkering project, that won't happen until the weather warms up, if prices aren't tooooo high.... my initial research on dimensions (always the first hurdle and usually a big one) show that the Weber IDF 40 are very similarly sized to the Mikuni's, and it appears the distance between the Yamaha centerlines and the Weber centerlines may only be about 7mm.

Interesting note, the responses here at WG were much more knowledgable and reasoned than the responses from the TDM850 & TRX850 Facebooks pages.  While the responses from the TDM & TRX websites were almost zero.

Old guys kick butt!

thanks again.