OK, so yesterday I bit the bullet and fitted my new carbs, twin dell 40's set them up on the bench as per the book. Took a while to get the fuel to them, but once it arrived they fired up, some pops some back fires and idling about 1500. So they are currently set up 30 vents 122 mains 9164.2 emulsion 180 Aires 58 idles 35 accelerator Running on a 2.0 cj In the tool box I also have spare 28 vents 118 mains 2x 9164.1 2x 9164.3 55 idles I am finding that I can't get the idle speed down using the mix adjustment and the idle screws were set with the butterfly set at three thous open. Am I OK with the current set up to let the engine warm up, or am I going to be running it too lean and burn out the heads? Help.....
from memory the 3 tho is just to get you started , I take it you set the float heights as this is megga critical ? use a flow gauge to sync both carbs and turn down iddle screws . Also megga critical that both carbs open at the same time ( you need a decent linkage ) . I have a 1700 with dells and have 28 vents so you should be good with 30`s although i would say your main jets are way small . I`m running 124 so at a guess you want 130 -135 but you won`t really know that until you drive it or get it rolling roaded .. just my thoughts
Thank you! Floats set up and with new Vinton needle valves I put the 122 mains in as that was what eurocarb suggested, a rolling road session is on the cards, but they are in illchester so about a 30 mile drive, which could destroy the engine if running lean! Have a cb hex bar linkage, not had a good session getting them dialed in yet, hopefully over the weekend, just needed to hear the engine start... Glastonbury is in a few weeks and still have a lot of work to do!
I had trouble with my CB linkage and had to do a few mods on it ,also its a nightmare to adjust using the left/right handed threads so I used a lever that uses the original carb adjusting screws .there is a lot of variables but the dell book is good ..... Take it for a spin see what it drives like ... I have a few sets of larger gets if you get stuck to borrow/try.
Cheers.... Might take you up on that offer... If it is running lean...how long before I do it any damage?
Should I be adjusting the air bypass when setting them up, or just leave that one screwed in tight and use the mixture control screws and speed control screws, sorry for all the noob questions!
the four air bypass screws at the bottom of the carbs just let you fine tune each barrel , i`d adjust the idle with the idle screws checking with the sync gauge ,
Got the idle down to something a little more sensible, not messed with the mix yet, seems OK, but that is just revving it on the drive, think the mains are a little small, at higher revs it didn't seem as well and I got some whistling from the carbs, not sure what revs it was at as the rev counter isn't connected yet! When I get some time over the weekend will try take it out for a spin!
They can whistle , you can get the proper anti-whistle plastic gaskets from the US or if you do a search on VZI they say you can plug certain holes to stop it , OR it could be the Venturi 's are too
Small ........ The vents are a cast item and the tolerance between the machined body and the cast Venturi can sometimes be such that they vibrate or whistle as the air flows through them ....
Was on tenterhooks there. Whats the fix? (I ask as Im watching with interest as will be going down this route shortly).
Are the velocity stacks necessary? I dont have them. Are they to reduce spitting back from the carb, lengthen inlet tract?? Ive got the tall fanny mould if that makes a difference?
According to the dell book the stacks straighten the air flow through the carbs , do they make a difference ? Not sure i can tell any improvement . I reduced the 'one size fits all' hole in the filter bases as well so from stacks to Venturi it's all the same size .I used the bog standard type 4 manifolds . My Venturi s were home made as were the stacks
Mmmm, Dells...I can smell them from here. They are magnificent . I'd resist fiddling with the small bypass adjusters - they're really only intended for fine tuning, as I understand. The stacks as lhu says are to straighten the airflow into the carb, so it rockets down through the venturis. And they look damn cool . They also contain the "upstand" when the carb's sucking: that strange area of mist that forms above the carb. I've heard of folk using cut lengths of exhaust pipe as cheap & cheerful alternatives. Apparently, the curved edges aren't that important.
Well they are in and running ok(ish) bit rich I think, tho not sure what is going on with no 1 after running for a few mins, if I touch the manifold nuts, 3 is hot, 4 is warm, 2 is warm ish and 1 is cool... But sounds ok got rid of most of the pops and bangs, not driven it out yet, currently stuck in Dublin for two weeks for work, very inconvenient!
