March 31, 20177 yr comment_516872 I'll also say that it's a linkage issue?Are you watching the ends of the butterfly at the carb body and seeing motion while working the linkage. Like said above - if no suction(air) , no boomSent from my iPhone using Classic Zcar Club mobile Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516872 Share on other sites More sharing options...
March 31, 20177 yr Author comment_516877 Thanx to everyone for the replys. Mark, Yes, I have flow in the rear carb and I also made sure the chokes were moving smoothly up and down with the lever. Yes pushed up on jets to verify closed when choke is off. Captain Obvious, Chickenman, Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little desitation and the pistons move like they should. madkaw, I am going to re check the throttle plate movement and make sure the needle and float aren't intermittently sticking shut. I have a few extras to try, it cant hurt, just have to verify float level every change.  Thank you to everyone for the help, I will let you know what I find.                  Jeff Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516877 Share on other sites More sharing options...
March 31, 20177 yr comment_516882 11 hours ago, madkaw said: Cliff, Your not really running that filter are you? Sent from my iPhone using Classic Zcar Club mobile Yes, without failing.  Ran one on my EFI too, no leaks at 32psi.  I recoated the tanks and wanted to see what was flowing through, no pink gas yet.   I've never had a problem with those filters. Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516882 Share on other sites More sharing options...
March 31, 20177 yr comment_516889 2 hours ago, JeffMopar said: Thanx to everyone for the replys. Mark, Yes, I have flow in the rear carb and I also made sure the chokes were moving smoothly up and down with the lever. Yes pushed up on jets to verify closed when choke is off. Captain Obvious, Chickenman, Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little desitation and the pistons move like they should. madkaw, I am going to re check the throttle plate movement and make sure the needle and float aren't intermittently sticking shut. I have a few extras to try, it cant hurt, just have to verify float level every change.  Thank you to everyone for the help, I will let you know what I find.                  Jeff  If the pistons are rising equally, I think the butterflys must be opening. It would seem (IMO) that the problem is in either in the linkage, (doubtful) or it's just a basic "out of sync problem". Have you tried going through the synchronization procedure again? Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516889 Share on other sites More sharing options...
March 31, 20177 yr comment_516892 Quote Captain Obvious, Chickenman, Yes I have the Unisyn balancer. Both carbs are adjusted to equal flow. I think that should have to mean the throttle plates are open close to equal. When I rev the engine it revs up fairly smoothly with a little hesitation and the pistons move like they should. " Revs up fairly smoothly and pistons move like they should " ... contradicts the subject line and main premise that the engine is only running on one carb. That tends to lead us all on a wild goose chase?? Sounds like it's actually running on both carbs, but not properly. Synch them again and check that the pistons are free. Remove both oil dampers. With engine off, lift each piston to the top position and then let it drop. It should move freely with no sticking and should drop freely and stop with a solid " clunk ". If there is any binding, remove the Piston cover and make sure jet is centered in jet holder. Check needle to see if it is bent or has score marks. After making any necessary adjustments. Replace the Piston cover and lightly tighten screws. Do the lift and drop test. If any binding, slightly reposition dome cover. There is some assembly variance built in.  Make sure dampers are filled to the correct level with lightweight oil ( I prefer ATF ) and reinstall dampers. Re-synch carbs. Edit; Be sure to check for any vacuum leaks around intake manifold. Loose Intake manifold bolts, split hoses etc. A Vacuum leak will put the carb synch out of whack. Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516892 Share on other sites More sharing options...
March 31, 20177 yr Author comment_516893 Just came in from the garage to have lunch. Started from the beginning and adjusted the RPM at full choke to 1450-1500 and made sure the carbs were balanced. Went through the full Syncing and Balancing process again, same results. Felt like no matter what I did the back carb wasn't getting fuel. Pulled the vent bung off to look inside the float body and used the WD-40 straw to push the float down, fuel immediately filled the bowl and overflowed. So I revved the engine to draw down the fuel level but the fuel didn't go down as much as I would think it should. I am going to pop off the choke linkage from the jet when I go back out and check to see if fuel is flowing freely through the hose from the bowl.    Jeff Chickenman, you posted just as I was. Pistons are free and moving as they should, needles are not sticking. Checked manifold and carb bolts and sprayed to look for vacuum leak, nothing. Lifting front piston immediately stalls down engine lifting rear does absolutely nothing also covering air flow with my hand doesn't get any response that is why I think there is no fuel flowing as it should. Adding a pic in case anybody sees something obviously stupid that I missed. Edited March 31, 20177 yr by JeffMopar Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516893 Share on other sites More sharing options...
March 31, 20177 yr comment_516894 Is there suction when you cover the rear carb with your hand? What to the plugs look like? Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516894 Share on other sites More sharing options...
March 31, 20177 yr Author comment_516895 240260280,  Yes to suction, I will pull plugs when I get back out there. Thank You,   Jeff Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516895 Share on other sites More sharing options...
March 31, 20177 yr comment_516898 You've checked the supply line from Float bowl to nozzle that it's not collapsing ?Sent from my iPhone using Classic Zcar Club mobile Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516898 Share on other sites More sharing options...
March 31, 20177 yr comment_516907 My interpretation of the problem is "I'm only running on one carb at idle. Above idle, everything seems to be OK, but at idle the rear carb doesn't do anything." Is that correct? What was the throttle position when you synced the carbs? Do you use one of the adjustment screws to raise the RPM's to something above normal idle while you are performing the sync procedure? If that's the case, then your carbs may be perfectly balanced at a higher RPM (wider butterfly opening), but at dead closed idle, your rear butterfly is too far closed for the carb to work. Did you manually open the butterfly on just the rear carb with your finger while at idle? What happened? Did the RPMs go up? Did you or someone mess with the "do not adjust this" stop screws on the carbs? Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516907 Share on other sites More sharing options...
April 1, 20177 yr comment_516929 When you cover the rear carb with your hand does fuel get in the air horn and on your hand? Try turning the base idle screw in the rear carb in (the "do not adjust this" screws, as CO calls them) a turn or two. Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-516929 Share on other sites More sharing options...
April 2, 20177 yr comment_517006 Sorry to ask the obvious but you checked your getting spark on those 3 cylinders? Link to comment https://www.classiczcars.com/forums/topic/57389-only-running-on-one-carb-help-please/?&page=2#findComment-517006 Share on other sites More sharing options...
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