Joe 90 Posted January 5, 2021 Share Posted January 5, 2021 Guys, my vitesse 2 litre lump is very difficult to start from cold, I have rebuilt the carbs and once warm it runs fine. I am used to SU carbs where the choke is more normal !! but these stromberg cd 150 (twin) have an unusual mechanism that I don’t understand. When the engine is warm the choke does not alter the running so I am guessing it’s not working at all. Any advise or reading matter on the subject gratefully received. Quote Link to comment Share on other sites More sharing options...
glang Posted January 5, 2021 Share Posted January 5, 2021 It depends which CD150 you have as theres different choke mechanisms used. If theres a cable that rotates a spindle running through the entrance of both carbs this should operate what people call a Thames Barrier in both carbs which can be seen in their mouths if you remove the airfilter housing. This lifts the air pistons/needles a little so enriching the mixture while an external cam pushes on the throttle spindle behind to raise the tickover. If the choke is operated with the engine warm it should certainly have an effect - initially the engine revs will increase and then struggle to run as the mixture become too rich. Quote Link to comment Share on other sites More sharing options...
Rutty Posted January 5, 2021 Share Posted January 5, 2021 Have you got the fast idle cam set right. The first 5-10mm of movement on the choke cable should only operate the fast Idle and not increase the richness of the mixture. Only after that should you see the cams in the throat of the carbs start to turn. Even when warm you should be able to pull the choke out 5-10mm to increase the RPM without upsetting the mixture. Handy when at stopped with the lights and fan on. Mark Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 5, 2021 Author Share Posted January 5, 2021 The choke cable operates a mechanism on the side of the carbs, not a spindle with disc on running through the carb to restrict the air like some. Yes the tickover cam is set right. I wonder if the choke mechanism is built correctly, discs inside with various holes in???? Quote Link to comment Share on other sites More sharing options...
glang Posted January 6, 2021 Share Posted January 6, 2021 Your car wont start from cold very well with just the tickover increased - it must also have the air pistons with their needles raised by the choke mechanism to richen the mixture. If when looking in the mouths of the carbs you cant see this happening then something is wrong Quote Link to comment Share on other sites More sharing options...
RobPearce Posted January 6, 2021 Share Posted January 6, 2021 It's not air pistons raised, glang. John has described what sounds like a later CDSE carb. In that case, it's most likely the choke mechanism has been rebuilt with the disc backwards or the link pipe is missing/blocked or some other such. Photos would help! Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 6, 2021 Author Share Posted January 6, 2021 Rob, I think your right, when I thaw my fingers out I may go and look. It’s a major problem as unlike a “proper” vitesse with opening front end and a handy tyre to sit on my kit car (gentry) has virtually zero room to work on the carbs!!!! Quote Link to comment Share on other sites More sharing options...
glang Posted January 6, 2021 Share Posted January 6, 2021 Ahhh that would explain it. Dont know much about those Im afraid except that the running mixture is adjusted with a specialised tool through the top oil dashpot rather than underneath the body. Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 16, 2021 Author Share Posted January 16, 2021 Right, removed both carbs (and knuckles) and they are 150 cdse types, one choke disc had been put in backwards and I cleaned them within an inch of their lives blowing all fuel ways clear. I also adjusted the float levels as another source said this was critical. I have another problem now, first carb was ok but I cannot centralise the jet in the second carb without it fouling some how. I have checked the needle is straight and rechecked assembly several times. The piston will not seat with a clunk if the jet is anywhere near the needle. With the jet assembly removed the needle appears central. If I remove the dash pot it seats ok but if I remove the jet it also seats ok. I am at a loss what to do next, any suggestions chaps? Quote Link to comment Share on other sites More sharing options...
glang Posted January 16, 2021 Share Posted January 16, 2021 As I say Im not used to your type of carb but Ive had a problem in the past where the needle position gets moved as the dashpot is bolted down. You could try putting the dashpot on losely and then doing up each of the screws a little at a time while lifting and dropping the piston. You might find the piston starts binding because the dashpot distorts slightly as its tightened... Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 16, 2021 Author Share Posted January 16, 2021 Thanks gang, Right, success, I turned the dashpot round (the same as the photos in the manual), did the screws up loosely one by one whilst flipping the piston up and down and after several attempts it did not bind. Something must be slightly warped but at this age (so am I 🤣). Tomorrow we will see of it starts (properly) 🤷♂️ Quote Link to comment Share on other sites More sharing options...
glang Posted January 17, 2021 Share Posted January 17, 2021 one thing, the 'tabs' of the rubber diaphragm are engaging correctly with the corresponding slots in the dashpot and piston arent they? If the dashpot one moves out of place your then trying to crush the thicker rubber while doing up the screws which may well cause misalignment.... Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 17, 2021 Author Share Posted January 17, 2021 Yes mate, did spot that, busy today but tomorrow I will connect the ancillaries and see if it starts properly (choke working). 🤞 Quote Link to comment Share on other sites More sharing options...
Joe 90 Posted January 23, 2021 Author Share Posted January 23, 2021 Right, finally got to connect everything up and she started first time, yet to tune the carbs properly (when it’s warmer). So one choke mechanism was built wrongly but perhaps giving them a good clean helped as well. Thanks guys fir your help. Quote Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 2, 2021 Share Posted February 2, 2021 one thing that can affect piston drop is aftermarket diaphragms made of thick stif rubber they should be thin gossamer , not recycled elephant condoms . the needles will be biased (sprung) so they wont /cant be centralised do have a look if on the side you the small platsic covers temperature compensators only 2 screws to remove them but they need to be adjusted so at normal temperature the small valve is fully shut , this add a bypass air past the throttles to weaken hot mixtures , if this little sod is open when it should be closed you will never set the idle mixture adjust the small nut to shut the ruddy thing for good, its a emmission aid thats a pain the housing has 2 0 rings to seal it to the body these disintegrate and leak air one simple dodge is turn the carb to manifold gasket upside down and you effectively delete the TC operation and any unscheduled idle air bypassing . set the needles with the small delrin washer just level with the base of the air piston thats the factory set , if its proud or recesses somethings wrong Pete Quote Link to comment Share on other sites More sharing options...
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