Anyone Know about Weber Carbs?

[Blake]

Hey Everyone,

was looking around this morning on the net when i came across some hot rod shop with lots of weber carb parts.  one of those were "chokes" as they put it.  

http://www.tperformance.com/street_rod_store/5200/chokes

Which very much look like venturis to me.  but as i was looking.. i noticed that the carbs such as the 44idf had "chokes" for 32,34, and 36mm..

then i came across this site:

http://www.webercarbsdirect.com/venturis__choke_tubes_

"Main ventures"

now.. i always was under the impression that, for instance, the weber 44IDF carb was 2 44mm downdraft carbs.  (ive always dealt with mikuni carbs myself, never automotive carbs)

now maybe someone can help me out here.  As you all know was was going to buy a pair of mikuni flatslide carbs (side draft) to put on my bike (was going to place order week after next)..but then i came upon this information...  weber downdraft carbs... now the adaptation wouldnt be a problem (would fab up some sort of intake manifold.. hmm..do you think a set of webers and airfilters would fit?)

anyway.. my questions to those of you that are more knowledgable than me.

1.  would weber carbs work on the vision?  (34-38mm venturi?)
2.  how well would weber carbs work in terms of perfomance. (better, worse, etc)
3.  Since ive never seen a weber in person.. is it small enough to be able to fit in the current space, and have an airfilter ontop? (either k&N pods, or single big k&n.. would probabaly rather go with individuals..or would single be better? i would think individuals wouldnt allow one carbs to suck more air out..like our airbox does now
4.  Weber.. or stick with the flat slides ??

As you can tell.. i know little about webers, but if you guys think a dual weber setup would work (and let me know what size/ model weber i should use).. im just looking now..and e-bay has a bunch of used ones for around 100 bucks a pop. (new webers going to run near 400, new dual Mikuni Flat Slides will be about 250-300)


Thoughts, comments, help?


Blake

[RobTx]

Don't know about Weber carbs specifically.  That being said, here are some thoughts.  Smaller venturies (what they call chokes) will give you better drivability at the expense of some top end horsepower.  My guess is that 32mm or 34mm would give you the best overall performance.  Remember that with short intakes, like k&n filters and big venturies, you will not get the air velocity needed to properly atomize fuel.  That seems to be the problem with the stock carbs, hence the flapper that doesn't open up until higher rpm's.  At just over $20 a pop, interchangable venturies sounds like an interesting thing to play with.  Del Orto makes a similar downdraft carb for VW's (old style air cooled), double barrel one for each side.  These sell on ebay really cheap too.  I've been tempted to experiment with them.  Some guys on the XS650 board use a single side draft SU originally made for Harley's.  They say it's a very easy carb to tune.  They look weird and you'd have to make a two into one manifold for it too.  In my opinion, a single carb with a 2-1 manifold would be the way to go.  Easy to tune, one set of jets, etc.  Doesn't have to be much bigger than dual carbs (I think a 38mm or 40mm would do it) because the cylinders don't fill at the same time.  A 48mm would flow as much as two 34's, but that would be way too big.  Here's an example of the Dellortos: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2453792646&category=33550
Venturies changable from 30-34mm.  I've seen them cheaper than this, this is just an example of what I'm talking about.  I bet you could find a pretty cheap set if you hooked up with a local VW bug collector.  Like I said, just some thoughts.
Rob

[Blake]

Hey Rob.. since you seem to know your goods..

when you say "Remember that with short intakes, like k&n filters and big venturies, you will not get the air velocity needed to properly atomize fuel. "  ...a question pops to mind.

i always was under the impression that the closer to the intake port the carb was, the better. and that the further away it is.. that your going to have a LONG lag...worse than our 4-5k rpm one...  but from what you say.. i can understand that a longer intake port would allow more time for the air fuel mixture to properly atomize..

so..question...  would it be better for me to space the carbs further away from the intake?  eg...

http://www.markvanderkwaak.com/dbbp/index.html  

now would it actualy be better for me to do something like that?  have the carbs sitting propped forward..even for a bit of ram air effect? (use velocity stacks with minimalist filters on the end...one of those links in the last post had them for webers.)   i always wanted to do this..especially with the flat slide minukis.. one on each side..   so i would assume the distance from the intake to the carb would be about 6-10" total..  do you think youd still get pretty good instant throttle response with that?


or another idea also come from harleys... same concept but facing up.

http://www.markvanderkwaak.com/dbbp/index.html



because if you can tell me that it would be better for me to actually space the carbs further away from the intakes than directly into the boots... that would help me out a lot..and..give me a lot more options..  


thanks for the help.

and sorry to everyone who thinks im a lunatic with all the questions ive been asking recently..  maybe ron should create a whole new sub section entitled "crazy blake ideas and questions"

haha


thanks again


Blake   (Found rim for chopper..  will hold a 120/90 - 21 tire.. bigger than the visions stock rear.. oh man..)

[Blake]

oops.. links didnt work..

First link was supposed to be to this:
http://www.markvanderkwaak.com/dbbp/index.html showing the first front facing version (one i like best out of the two)


second link to be this showing carbs away from intakes..and facing up.
http://www.markvanderkwaak.com/dbbp/cadbikes/cadbike04/carb.jpg



but would those be better, allowing it to have a longer intake tract giving the mixture more time to completely atomize?

then also..  regarding the forward facing one.. i was thinking.. have the carb (single on each side for example) running parallel to the bike (facing forward).. if i had a small section of pipe infront of it (or even a velocity stack) and put this on the front...think that would help?

http://www.knfilters.com/universal/X-stream.htm

or also what i was thinking which im pretty sure would work.. basically a semi ram air box..have the carb facing forward, thena section of pipe the size of the intake bell of the carb run say a few inches, then have that filter attached.. but.. have the filter surrounded by a bigger pipe.. basically like a MUCH bigger velocity stake that would help catch air and direct it into the intake port..



but point of this post...

would putting the carbs further away from the intake boots be beneficial?

and also

with the carbs away from the intake boot.. would it be alright to have the airfiter right on the carb? or should i place a section of pipe infront of it.. to help channel the air?  Im just looking for performance (not high performance.but better running) views..on which would be better..i can figure out how to mount it all later..thats the easy part..



thanks again,

Blake

[RobTx]

Sorry if I wasn't clear Blake.  I meant the intake from the carb bell to the air filter.  That's why velocity stacks are called that, to get the air going fast down the tube for better atomization.  The longer the intake track to the intake valve, the greater the chance for gas droplets to fall out of suspension, especially with curves.  I would guess that up to 5 or 6 inches between carb and intake with gentle bends would be ok.  But what I was talking about was from filter to intake side of carb.
Rob

[Blake]

Roger that..  thanks for the clear up.. i understand now





Blake

[RobTx]

Just poking around the webercarbsdirect.com website, I found this diagram of a 34mm Weber downdraft carb.  Looks a whole lot in basic design like the Vision carb, I'd even go so far to say it's a semi knock off.  
Rob
P.S. 300th post!

[Dan Byers]

If I remember correctly, that crazy Bernard LaJolie (or something like that) had fitted a pair of FZ750 carbs to a Vision with great success. details on exactly how that was done have (to my knowledge) never been discussed. I remember that dealing verbally with ol' Bernie was an excercise to say the least. Does anyone know how to contact him? I would think this would also be a thing to check out.

Dan

[Lucky]

you should be able to find his email addy if you click on "Members" above, then sort them alphabeticly to find his name.
--Lucky

[Rick G]

Rots of Ruck on getting old bernie to respond . I tried a year ago to get some information from him .  He never answered either email.

[rick_nowak]

weber IDF downdraft series uses mostly the same tuning parts as the DCO sidedraft series.  jets emulsion, tubes, primary and secondary venturis, etc.  my understanding of webers on motorcycle engines is that they are  impacted by vibration in a bad way more than carbs designed specifically for bikes, snowmobiles, etc.  that said, i have certainly seen pictures of installed webers, mostly DCO series and mostly on Harleys.  the instrument itself is about 50% larger in size than our revered Mikuni.  it could probably be fitted with vastly different manifolding and somehow jammed within the frame rails and the gas tank.  the gas tank would require serious surgery probably and of course the stock airbox would be out the window.
IDF's are used on mostly VW bug motors and similar Porches.There are many more DCO series carbs out there.  the problems of use are probably less but i would wonder about float bowls and motorcycle leaning and, of course, one crash on the right side could have very serious consequences.  As for the del orto's, they are sort of copies of the weber, same for similar Mikuni and Solex.

[Ken_Williams]

The Ducati Paso was sold with Weber carbs.....

[Rick G]

I under stand that they were a bear to tune on the Duc. and they discontinued using  them.