The Cal-look Lounge

Right guys I have a couple of questions for ya - Here goes  :)

1: I have just brought a coupke of rebuild kits for my weber40dcn's and the kits have 2 (two) different size accelerator pump diaphrams - the question is which ones do I use for my dual carb'd 1641 ??? (see pic)

2: Also on the accelerator pump - the arm that controls this diaphram has 2 (two) pivot points (holes) giving a different amount of movment on the diaphram - Question is which hole do I use  ??? I was using the No2 hole with my single carb set up just out of interest - this hole gives the most leverage/movement of the diaphram (see pic)

Let me know what you think guys :)

can you check against the size of the one already fitted, and use that?

dude you have answered the question yourself - I can't check against the ONE I am using as that was on a SINGLE carb, this is a DUAL carb setup I am talking about  :)

So Anyone  ???

My guess is the smaller diameter accelerator pump and position 1 (shorter stroke) on the arm :-\ :)

After looking at my GB tech manual, they only have 42 DCNF's

Now the schematic you have compared to theirs have two different sized acc pump diaphragm.

Your schematic uses the small one, theirs uses the large one, this presumes the rebuild kit is suitable for both makes of carb.

My Weber manual is packed away, so can't look at that.  I don't presume you have a part number?

Hmmm interesting - I see what you mean about my schematic it does look like the "smalller" diaphraGm ( ;))

I just took another look at my Rebuild kits and they are actuallly for "Weber40dcn 18/21" I think these are pretty much the same as mine just with a choke mechanism/flaps - they were used on Ferrari 246 Dino's

Notice in the schematic of the "14's" there is all the mechanism for the choke BUT No flaps :-\ :)

hey

i will check mine when i get home, but on top off my head i use the second hole. just be sure the arm is not toughing the diaphragm so it wont spill any fuel on the butterfies and give bad response and too much fuel consumption at idle...

not sure about which one you use, but it would make sense that you can do with less movement on the pumps as they now feed two cylinders insted off 4.

what type Diaphragm? i couldn't tell. but check the hight off the stems and see if there is a difference.

hope it helps a bit.

Hey dude - well here some more info just to confuse things  ::)

I have just rechecked the diaphragm I was using with the single setup and that is a different size from BOTH in the kits ::) BUT all the stem heights are EXACTLY the same :-\

The 3 (three) diaphragm sizes are as follows - top in pic = 18mm, bottom in pic = 26mm and my original single setup = 22mm

Also if you look closly there are two different "types" of diaphragm - the bottom/bigger one looks better quality with a carboard+rubber diaphragm (like my original) it seems to have much beetter movement/action - Hmmm too much to think about :-\ ;) :)

i would run the bottum one myself, but like i said make sure the pump arm has some freeplay or that the engine doesn't vibrate  ;)

Hmmmm been thinkin about the "freeplay" issue - if you notice there is a return type spring fitted under the the diaphragm to force it out against the arm :-\

I never had a problem with this on the single  :)

they all have the return spring and i never worried either until i ran the stock type3carbs without the filter for a testdrive and noticed every movement on the linkage or gentle tough made the nozzles drip. so i guess it is the same when driving. that is whhy i brought it up. and if you look at the DCNF tread a while back, there was also a mention off a 0.010 (or so) off freeplay on the diaphragm. so it makes sense to me. the rollers are even more sensetive i guess.