skinner2k3 3 Posted May 29, 2008 I have just bought a set of recently serviced weber 40s. They are presently set up for a 1.6 XU and I will be fitting them to a 1.9 XU. I know they will be towards their limit on a 1900 but it’s a std engine and 40s will take up to 36mm main venturis which according to research I have done so far should be more than enough up to a mild state of tune. From what I have read and calculated I believe I will be needing; 32mm or 34mm venturis Main jets around the region of 130 Air correctors circa 180+ Emulsion tubes F9 or F16 I know the carbs have 30mm venturis in at present, so I would assume the main jets may be a tad small. Hopefully I will be lucky and the emulsion tubes will be ok, I will probably go with whatever tubes they have to begin with and just see how the progression is. If it nose dives or hunts coming onto main I will go up or down a size accordingly. The above may be completely incorrect and any advice would be greatly received. If anyone happens to know proven jetting figures for a 1900 on twin 40 DCOEs I would love to hear them. Cheers Ben Share this post Link to post Share on other sites
skinner2k3 3 Posted May 30, 2008 OK Done a bit more searching and I will probably aim to start with 34mm, 140 or 145, 180, F16 How do you tell which jets, tubes etcs are fitted? I know the chokes have numbers stamped on them, but waht about the smaller bits? Cheers Ben Share this post Link to post Share on other sites
skinner2k3 3 Posted June 1, 2008 Have I just asked a really difficult or stupid question??????? Share this post Link to post Share on other sites
Baz 421 Posted June 1, 2008 No just one that not many people know how to answer. I'm sure there's a few threads with some info that could be useful, when i have a chance i'll try and find them if you can't. Share this post Link to post Share on other sites
skinner2k3 3 Posted June 1, 2008 Cheers, thought I had been sent to coventry I will keep looking, but I promise I have looked. Did find a couple of usefull posts mind. Share this post Link to post Share on other sites
puginfo 0 Posted June 3, 2008 the smaller bits have the numbers engraved on them as well. you need to pull them apart to check. check the idle valve as well. 145main, 200air, F16, 34mm choke would be good on the secondary. the nose dive you mentioned is a bad hand off between the primary and secondary ccts. get it started with what you have first and go from there. the distributor needs some work as well. if you are on the dcoe manifold, try to block off and work without the vacuum advance as it tends to fluctuate the idle. cheers Share this post Link to post Share on other sites
skinner2k3 3 Posted June 3, 2008 I have now had the jets out and checked which are fitted, all will be too small for a 1900. I have now read a fair few jetting options for a 1900 and as mine is pretty much standard will probably go for around 135main, 185correction, F16 emulsion. Our machinist at work is going to bore the chokes out to what ever I want, 32 or 33 probably. The problem I have at the moment is getting the chokes out. My fingers are niether long anough or strong enough to pull the chokes out. I have the Aux out and have checked my carbs do not have a retaining screw. Anyone have any usefull tips for removing chokes???? Share this post Link to post Share on other sites
puginfo 0 Posted June 4, 2008 I have now had the jets out and checked which are fitted, all will be too small for a 1900. I have now read a fair few jetting options for a 1900 and as mine is pretty much standard will probably go for around 135main, 185correction, F16 emulsion. Our machinist at work is going to bore the chokes out to what ever I want, 32 or 33 probably. The problem I have at the moment is getting the chokes out. My fingers are niether long anough or strong enough to pull the chokes out. I have the Aux out and have checked my carbs do not have a retaining screw. Anyone have any usefull tips for removing chokes???? have them immersed in fuel for the whole day and then with some WD40 spray soaking should have them apart. what use is this engione gonna be? race or road? important for the choke boring diam. is this a XU9 or XU10 setup? Share this post Link to post Share on other sites
skinner2k3 3 Posted June 4, 2008 Cheers will give that a go. I was also advised to put them in my oven, but I dont think the misses would appreciate that. They are being fitted to a 1900 XU9 engine, only changes from standard are a skimmed head and 4-1 manifold. Its a road legal track car, not used for daily commuting but I would like half decent tractability. I planned to choke it for a bit of extra oomph throughout the rev range as oppose to flat out top end. Hence I didnt want to go up to 34, but at the same time thought 32 might be a bit too restrictive. Seeing as I can chose the diameter I thought why not go in between What do you think 32, 33 or 34? Have you ran carbs on a XU9? Share this post Link to post Share on other sites
puginfo 0 Posted June 5, 2008 yes i run dcoe's on both NA and forcefed in my XU9. pic below. if yr XU9 was fuel injected, keep the ignition and design all else around it. if its a carby version then the dizzy would need some tweeking. a piper cam pulley would be needed to get the power range in where you need it. 32mm would be good till you discover more as you move along. Share this post Link to post Share on other sites
skinner2k3 3 Posted June 5, 2008 Wow, never seen that done before. At the moment the engine is a std 1900 XU9 with original fuel injection, AFM etc. So yeah, I will have to keep the ignition side of things. 32 it is then, better slightly under size than over I suppose. All I need to do now is get the buggers out! They were placed on their end and a good dose of WD40 sprayed round the venturi, hopefully they will budge eventually. Although I think I may resort to removing the throttle butterflies and spindle in order to knock them out with a bit of wood. Should I be cautious of that? I have heard they can be difficult to line up again after. Cheers Share this post Link to post Share on other sites
skinner2k3 3 Posted June 6, 2008 Woohoo, last night I got the chokes out and without removing the throttle spindle. Happy days! Just got to chuck em in the lathe now. I am going for 32mm. Share this post Link to post Share on other sites
