NickW Posted February 22, 2003 Share Posted February 22, 2003 Hello, Just tried out my Carbtune and colortune gear. The carbs were way out of sync, but adjusted them to within 2cmHg. Checked the mixture at idle with the colortune, No1 cylinder was ok, richened it slightly. But No2 will not richen, no matter how much I adjust the mixture screw, if I turn the screw all the way in then there is no flame, a few turns out and I get a yellow flame. If I keep turning the screw out, quarter turn at a time there is no change, the flame stays yellow. The colortune booklet says that the cause is probably a blocked idler jet. I have taken this out and it looks ok. Is it a carb off and strip down job or is there anything I can do with the carb on? Any suggestions (clean please) will be welcome. Thanks, Nick. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted February 22, 2003 Share Posted February 22, 2003 First question, are all the Air Bypass Screws set the same? I found on my Zetec that I could only acheive exact balance by tweeking these but there you go What puzzles me is you say you go from No flame to Yellow flame..thats a bit strange. Whith the CLEANED Colortune in wind the Mixture screw all the way in to No flame then tiny bit by tiny bit wind it out until it can be seen that the cylinder in question is firing every time and is a nice bunsen blue It can be really quite little movements that you need to get it right Or it may be that your jetting is so far out that it won't come into range but it sounds a bit unlikely to me As a general tip I found for really sweet running dont just set balance at idle, also set it at say 3-4k by putting in a temp long idle speed screw. Wait till next door are out for this one though! It is a real challenge to get good balance at 3-4k as well as at 900 See My Zetec Power 7 Here Link to comment Share on other sites More sharing options...
NickW Posted February 23, 2003 Author Share Posted February 23, 2003 There's a saying in the computer industry ( and probably other places as well) RTFM - I did and now understand what I am supposed to do with the mixture screw!!! DOH DOH DOH *confused* *confused* Successfully balanced and tuned and what a difference. No blow back in the carbs and much stronger pull through the gears. Nick. Link to comment Share on other sites More sharing options...
Casbar Posted February 23, 2003 Share Posted February 23, 2003 Steve, How do you balance your carbs at idle and 3-4 k then? To balance the carbs you adjust the linkage screw, so if you balance at idle (should be done at around 1500 rpm), then you go to 3-4k and balance, then you have just adjusted the same screw that balanced the carbs at idle! Or do you mean, check the balance at 3-4k as well! Or is there another way to balance the carbs! Link to comment Share on other sites More sharing options...
puremalt Posted February 24, 2003 Share Posted February 24, 2003 yeah, how do you do it as I'm about to undertake this myself? Mine Farts and Belches Link to comment Share on other sites More sharing options...
puremalt Posted February 24, 2003 Share Posted February 24, 2003 I also forget to say that the synchrometer that I got from Burton has no indication of what figure the carbs should give. I assume all I have to do is to get an equal number from each trumpet???? Mine Farts and Belches Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted February 24, 2003 Share Posted February 24, 2003 Casbar My personal feeling is that your carbs should be in balance from idle all the way through to WOT but how many people ever check anything other than idle? Im the only person I know. Over about 3.5 k ish you move from the idle jets to the mains so if you can stand the noise, pop in a really long speed screw and gradually wind the butterflys open poping in your balancing tool at various revs up to as high as you like(dont take to long its probably not good for the engine) if its a good one like mine you might just notice like I did that the between the pairs the carbs were definately out. Not by much but a bit, a noticable bit. Across the venturies they were perfect which is just as well because you cant change that anyway. I re set them and tested a load until I was happy that at all throttle openings(seen less as the throttles are opened wider and wider) they were all flowing the same and then came back to the 900 rpm range, which you guessed it was now out.... a bit (its all about the bits isnt it!). What I found was that with very careful adjustments of the Idle bypass screws I could dial them in at this range as well. Hey presto! Perfect at all revs No one ever seems to adjust these screws, prefering to leave them at the usual 2 turns out or whatever they are supposed to be to start with but I figured they were obviously put there by Mr Webber for a reason and I found a reason to twiddle them. Try it for yourself, I might be talking technical crap but it worked and made sense for me and my car runs lovely, if you dont check it you will never know. HTH Steve See My Zetec Power 7 Here Link to comment Share on other sites More sharing options...
Casbar Posted February 25, 2003 Share Posted February 25, 2003 I maybe talking rubbish as well, but my understanding is: The carbs should be balanced off idle, ie after the idle screws and jets have finished their job (around 1500 - 2000 rpm). Then the carbs are in balance. If any of the chokes are out, then there maybe a spindle problem. If you adjust the idle (mixture) screws and balance that way, you are just adjusting each choke for mixture (rich or lean). The object is to make sure the air flow through each carb is the same when off the idle screws, and the ignition is advanced. Link to comment Share on other sites More sharing options...
ian balson Posted February 25, 2003 Share Posted February 25, 2003 Steve, Do you mean the "Air by-pass" screws as opposed to your post that mentions "Idle By-pass" screws? I can understand that you could perform some balance function at Idle using the Air By-pass adjustment, but I though these were meant for fine tuning balance between the intakes on a single carb, and were preset by the factory, hence the plastic cover? Rgds Ian Link to comment Share on other sites More sharing options...
Casbar Posted February 25, 2003 Share Posted February 25, 2003 Seems to be a bit of confusion around terms! Ian, do you mean the "Progression hole inspection covers" which have screws in them! If so, the covers are there to allow progression holes to be drilled in the carb body, but also doubles as a removable plug for cleaning, or checking to make sure the holes are clear. On my understanding there is nothing there to adjust though! Link to comment Share on other sites More sharing options...
ian balson Posted February 25, 2003 Share Posted February 25, 2003 Casbar, No, not the progression hole covers, I mean items 25-26 on the diagram here I'm not sure all models of DCOE have them, certainly my 45 DCOE 152's do. Cheers Ian Link to comment Share on other sites More sharing options...
Casbar Posted February 25, 2003 Share Posted February 25, 2003 ian, I see the ones your on about now. Didn't know you could adjust those Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted February 25, 2003 Share Posted February 25, 2003 Ian Sorry, correction, Air by-pass screws It just seemed to me that air bleeds past these at low idle speeds and if at these speeds the carbs are not in balance as one is bleeding more than another then it cant be a good thing and misleading for balance in general. If balance is done when these play little part in the equation overall ballance has to be better? Makes sense to me and then you come back down the rev range and sort out the balance at low tickover with the Air bypass screws Someone else go and have a play and see if you found what I did Steve. See My Zetec Power 7 Here Link to comment Share on other sites More sharing options...
ian balson Posted February 25, 2003 Share Posted February 25, 2003 Steve, How are you measuring the vacuum? If you are using a Carb Sychroniser that you push into the trumpet, I don't think you'll get a clear reading, as the air-bypass valve feeds air into the engine side of the throttle butterflys. If you are taking a reading from the Vacuum take-off holes you should get a true reading of the balance behind the throttle butterflys. But if what you are doing works, then stick with it ! Rgds Ian Link to comment Share on other sites More sharing options...
Casbar Posted February 25, 2003 Share Posted February 25, 2003 Ian, Just spoke to roger K, to clarify things for my own unsterstanding. He told me to only synch the carbs at idle as at full throttle the opening will not make that much difference. (Great advice when you think about things and how carbs work) He also told me that the screws you were on about can make a difference to single chokes, but you should only adjust one, or you will be trying to balance against a false reading (ie, leave the lower one fully shut home and adiust the other of the single choke, to make them the same. As for the tool to use, the synchrometer which is pushed into the trumps is fine and does give a accurate reading, as all you are trying to achieve is the same airflow. But hey what do I know, can't argue with a carb expert Link to comment Share on other sites More sharing options...
ian balson Posted February 26, 2003 Share Posted February 26, 2003 Casbar, Good ! That's in line with what I've been doing, I've only ever adjusted the Air by-pass once to calibrate the chokes on the single carb, and then balanced the pair at 1500rpm. See you on Tuesday. Cheers Ian Link to comment Share on other sites More sharing options...
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