AarhusTr6 Posted June 23, 2021 Report Share Posted June 23, 2021 Hi all I have recently had my carburettors completely rebuilt and refurbished by a professional company in Germany. Overall the car is now driving really well but I just cannot get the idle below 13 1400.. The idle screws are completely out and I cannot find the choke is ion. I have even gone as far as dislocating the linkage but it's still will not go 13 to 1400 RPM. I do not think I have left any hoses open or have any leaks so I'm getting really stuck. Richard Quote Link to post Share on other sites
harlequin Posted June 23, 2021 Report Share Posted June 23, 2021 Hi Richard Maybe the butterflys are not centred in the carb body, it will mean taking the carbs off again to get a clear view down the choke George Quote Link to post Share on other sites
John L Posted June 23, 2021 Report Share Posted June 23, 2021 What happens if you disconnect the breather pipe from the rocker cover and plug it, so not letting in any air from the engine. Can you blank off the pipe to the brake servo, tell us what happens to both items. Could also be the bypass air valve needs setting, see page 27 on here, https://www.triumphwedgeowners.org/uploads/3/0/4/2/3042952/_zenith_stromberg_factory_tuning_manual_-_complete.pdf John Quote Link to post Share on other sites
poolboy Posted June 23, 2021 Report Share Posted June 23, 2021 That is about high high the idle would be if the Throttle Bypass Valves were open....If you find nothing else check that out. And since it is basically considered an "Emission Control" ancillary component, it can be disabled with affecting performance. The most common and permanent method is to make a solid gasket with only enough holes for the 3 screws that attach the TBV housing to the body of the car and thick enough to withstand very high vacuum of at least 22 in-Hg. A less than permanent method would be to turn the TBV spring tension adjustment screw, if it's exposed, CounterClockWise until it stops. Quote Link to post Share on other sites
poolboy Posted June 23, 2021 Report Share Posted June 23, 2021 And ,btw, that nipple with the black cap sealing it is not a good idea....on those carbs that nipple serves 2 purposes, but the one that is important is to provide ventilation for the carbs' float chambers when the engine is idling...without that vent the fuel flow into and out of the float chamber will be affected adversely. This nipple..red for identification; Quote Link to post Share on other sites
AarhusTr6 Posted June 24, 2021 Author Report Share Posted June 24, 2021 8 hours ago, poolboy said: And ,btw, that nipple with the black cap sealing it is not a good idea....on those carbs that nipple serves 2 purposes, but the one that is important is to provide ventilation for the carbs' float chambers when the engine is idling...without that vent the fuel flow into and out of the float chamber will be affected adversely. This nipple..red for identification; Hi Ken (I think I got your name right??) The PO had pipes from hear running to the cannister in the boot/trunk (not 100% sure until I jack car up properly) , I cannot say I fully understand his logic as when I blew down the pipe. it had little to no air movement. Note, carbon cannister is well gone. If I do put breathers onto these, where do the run to? Thanks, Richard Quote Link to post Share on other sites
poolboy Posted June 24, 2021 Report Share Posted June 24, 2021 Yes, it's "Ken", thanks. The vent line from the fuel tank has to remain open either to a Carbon Canister for vapor absorption or just open to atmosphere. Otherwise fuel flow to the fuel pump will be restricted and eventually interrupted within a few miles of driving. Open the gas cap on the tank and blow air into the vent line in the direction of the fuel tank. You should hear the air enter the tank. As far as the 'red nipples' it depends. I just left mine open to atmosphere. Some fear that a carb malfunction causing the carbs to flood would allow fuel to drip out of the red nipples.... and that does happen if the needle valves malfunction., so they stick hoses on the nipples and route the hoses forward, away from the exhaust as if they were going to a Carbon Canister. Quote Link to post Share on other sites
harlequin Posted June 24, 2021 Report Share Posted June 24, 2021 Hi Richard Why not reinstate the carbon canister it has a few advantages, such as no petrol smell in the garage, and an anti run on valve. Since I put mine back in I have not had the carb needle valve stick open once,an event that used to happen quite regularly. George Quote Link to post Share on other sites
peterq Posted June 25, 2021 Report Share Posted June 25, 2021 Hi Richard, I think the reason is the bypass valve. Please check if your carburettor has the screw as show on the picture. Some older carburettors do not have this crew on the outside. If the screw is there, turn it anticlockwise, as far as possible on both carburettors. By doing this you are tensioning a spring in the valve, which closes it. Now your car should idle normally. Disconnect the link on the butterflies, adjust the idle with the idle screws (opening butterfly) until 1400-1500 rpm. Then turn the bypass valve screw on the first carburettor clockwise. Suddenly the valve will open and the engine runs at 2500 rpm. Stop the engine, turn the screw anticlockwise 180 degrees and repeat this for the other carburettor. Synchronise both carburettors at about 1500 rpm, connect the butterflies and adjust idle. Regards Peter. Quote Link to post Share on other sites
harlequin Posted June 26, 2021 Report Share Posted June 26, 2021 On 6/25/2021 at 12:18 PM, peterq said: Hi Richard, I think the reason is the bypass valve. Please check if your carburettor has the screw as show on the picture. Some older carburettors do not have this crew on the outside. If the screw is there, turn it anticlockwise, as far as possible on both carburettors. By doing this you are tensioning a spring in the valve, which closes it. Now your car should idle normally. Disconnect the link on the butterflies, adjust the idle with the idle screws (opening butterfly) until 1400-1500 rpm. Then turn the bypass valve screw on the first carburettor clockwise. Suddenly the valve will open and the engine runs at 2500 rpm. Stop the engine, turn the screw anticlockwise 180 degrees and repeat this for the other carburettor. Synchronise both carburettors at about 1500 rpm, connect the butterflies and adjust idle. Regards Peter. Hi Peter Thanks for posting this you have encouraged me to get my bypass valves working properly George Quote Link to post Share on other sites
AarhusTr6 Posted June 26, 2021 Author Report Share Posted June 26, 2021 Well that was annoying. . . went to turn the screw on the bypass valve as suggested by Peter and the brass screw broke ! Not sure what to do now Quote Link to post Share on other sites
harlequin Posted June 26, 2021 Report Share Posted June 26, 2021 20 minutes ago, AarhusTr6 said: Well that was annoying. . . went to turn the screw on the bypass valve as suggested by Peter and the brass screw broke ! Not sure what to do now All part of the joys of old cars Take a deep breath, make a brew, take the valve off and strip down, order the parts and start again George Quote Link to post Share on other sites
AarhusTr6 Posted June 26, 2021 Author Report Share Posted June 26, 2021 4 minutes ago, harlequin said: All part of the joys of old cars Take a deep breath, make a brew, take the valve off and strip down, order the parts and start again George thanks., . I have sworn enough when it happened. . . ! Quote Link to post Share on other sites
poolboy Posted June 26, 2021 Report Share Posted June 26, 2021 1 hour ago, AarhusTr6 said: Well that was annoying. . . went to turn the screw on the bypass valve as suggested by Peter and the brass screw broke ! Not sure what to do now Don't worry about the screw, just make the "solid" gasket and disable the thing properly and permanently. Quote Link to post Share on other sites
peterq Posted June 26, 2021 Report Share Posted June 26, 2021 Hi Richard, strip down the valve, use a hacksaw to make the slot a bit deeper. Now you can see how it works. Ofcourse you can disable the valve, but I see no reason for doing this. There is a reason why the valve is there and disableing the valve does take the same time as making it functional. Not all repairs go without swearing, but this one is easy to correct. Regards Peter. Quote Link to post Share on other sites
harlequin Posted June 26, 2021 Report Share Posted June 26, 2021 Nothing is lost by trying to get the things to work. The valves on my car are disabled but I shall have a go at getting them working properly just so that I can learn a bit more about the car and if it don't work out I shall return them to the disabled situation. George Quote Link to post Share on other sites
poolboy Posted June 26, 2021 Report Share Posted June 26, 2021 1 hour ago, peterq said: Hi Richard, strip down the valve, use a hacksaw to make the slot a bit deeper. Now you can see how it works. Ofcourse you can disable the valve, but I see no reason for doing this. There is a reason why the valve is there and disableing the valve does take the same time as making it functional. Not all repairs go without swearing, but this one is easy to correct. Regards Peter. It might be a good idea to explain 'why the valve is there' Peter. Then people can decide if it's worth having and keeping, because one thing is certain...it will perish and then there will be more topics such as this "high idle". Quote Link to post Share on other sites
AarhusTr6 Posted June 27, 2021 Author Report Share Posted June 27, 2021 (edited) Morning all So I plugged the pipes from the manifold, ie to brake and the rocker and no difference. Getting a bit frustrasted now. I am concerned on a hot day, in traffic of too much heat, plus it is just too high (1400) so annoying. Richard Edited June 27, 2021 by AarhusTr6 Quote Link to post Share on other sites
peterq Posted June 27, 2021 Report Share Posted June 27, 2021 If you are driving fast or downhill, and suddenly close the butterflies, you will have a rich mixture and a large depression in the intake area. The mixture is too rich and will not burn in the cylinder, but explode in the exhaust with a popping sound. The bypass valve opens for a short moment at large depression to give more air to the rich mixture. If Richard had his carburettors refurbished, then the bypass valves will have been renewed. Why not make it work as it should? Regards, Peter. Quote Link to post Share on other sites
poolboy Posted June 27, 2021 Report Share Posted June 27, 2021 I wonder why they were not properly adjusted by the refurbisher ? You don't have to do it on a running engine. It's usually the middle of the screws' adjustment range plus 2 more turns of the screw in the CounterClockWise direction Anyone who does that work should know how to set them without having to mount them on a running engine....but over here where ZS carbs are the rule not the exception, it's a common practice not only by owners but also by the 2 largest ZS CDSE carb rebuilders to disable the TBV and the Temperature Compensators to make the carbs more like the pre emission ZS CD carbs...no harm and less to go wrong. And because they are disabled doesn't automatically mean the exhaust will pop or even gargle during engine braking scenarios. I understand your position, Peter; you are in favor of keeping the TBV active and properly adjusted and I'm not and made it known and neither of us are likely to change. The horse is dead, so I should walk. Quote Link to post Share on other sites
AarhusTr6 Posted June 27, 2021 Author Report Share Posted June 27, 2021 Dear all Can we assume, maybe that the bypass valve is not the issue? Went for a city drive and its just annoying and uncomfortable to sit at a traffic light at 1500 RMP .. is there anything else I can do? I hoped for a roadtrip in 2 weeks but this problem is putting me off Richard Quote Link to post Share on other sites
poolboy Posted June 27, 2021 Report Share Posted June 27, 2021 If it's not the TBV and it;s not a mechanical or some physical interference with the throttle linkage and it's not a major vacuum leak then look for smaller leaks....such as from the vacuum nipple on the underside of your carb. If your carbs are 71 versions, there would be a nipple on the bottom of the rear carb that needs to be tightly plumbed to the distributor or TIGHTLY sealed if the retard is disabled. Quote Link to post Share on other sites
AarhusTr6 Posted June 27, 2021 Author Report Share Posted June 27, 2021 Hi Ken The engine is a 74, so guess carbs are too. Also I am 99% sure there is not nipple on the underside of the carbs. Thanks, and getting a bit desperate to be honest as was hoping for a roadtrip to Germany in 2 weeks but I not keep to do this with this underlying issue. Richard Quote Link to post Share on other sites
poolboy Posted June 27, 2021 Report Share Posted June 27, 2021 If the carbs are 74, then there will definitely be that nipple on the front carb...bottom as shown. Quote Link to post Share on other sites
Peter Cobbold Posted June 27, 2021 Report Share Posted June 27, 2021 maybe the diaphragm in the retard capsule on the disy is punctured ? Quote Link to post Share on other sites
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