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  1. #1
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    On taking my DS for a short(6km) run yesterday to see if the overheating problems were cured(they were not!) I found that every time I put the brakes on the engine died. As this is a BVH applying the brakes reduces the idling revs. I checked both idling jets and they are clear. Since the engine ran normally I have not touched anything other than cooling system.
    Any ideas would be most welcome.
    Don

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    Don't drive a DS during a heatwave???

    It should creep forward a little at idle, but should not stall when you stop. So, you might need to look at the adjustment of the clutch engagement. There's a specific process to follow. Or the carby ... or maybe it was simply the heat?

    How have you determined that all the parts of the cooling system are OK? It's fairly basic, so it will be something like a failed thermostat, blocked radiator or bypass hose or a water pump with a corroded impeller. If I remember correctly, you had an additional cooling fan. Does it operate correctly and in the correct direction? Does it make any difference?

    What sort of coolant are you using? If you use too little water, the capacity of the coolant to cool is greatly diminished. That is why waterless coolants need other tricks to work. Perhaps, drain it and try it on straight water as a test to see whether the coolant could be part of the problem. Maybe, descale the system? Straight water is the ideal coolant, but obviously has a corrosion problem and can't be used as such.

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    You live in Adelaide and you drove a DS yesterday?!?!?

    I nominate you for either a bravery or Darwin award. Please take your pick!
    Craig K
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    Your symptoms would suggest to me that what ever you have disturbed during your cooling system overhaul has affected the relationship between the normal idle circuit & the brake controlled accelerated idle valve. I am thinking that previously too much idle air was being sourced through the accelerated idle valve.
    Check this by closing off the accelerate idle valve completely and setting the idle with the butterfly before resetting the valve for the extra 50 rpm with foot off the brake.
    If your car is injected, check that the idle circuit hasn't carboned up by removing the large idle adjust screw & running a smokers pipe cleaner through the ports.
    If your car is carburettor, has the manifold drain tube under the carburettor been blocked accidentally & the accelerated idle valve been adjusted to compensate.
    Is it possible that the throttle cable was not seating properly before & is now accidentally sitting correctly allowing the throttle to close properly ?
    A manifold air leak accidentally cured during your cooling system repairs is another avenue to investigate.

    Just a few ideas that I hope may help.

    Keep having fun.

    Richard

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    Thanks for your ideas David. I drove it in the morning and the temp was quite mild (i.e. less than 40) I had previously had big problems trying to get it not to stall under brakes but for the last year or so it had been fine.
    Since I bought this D over 2 years ago virtually everything thing has been done to fix the o/heating - rebuilt radiator, new hoses, new thermostat (checked out OK yesterday,) & waterpump The electric fan works only by a switch, but makes little difference & does turn the right way. I have just used the expensive 2 part cleanout system (something like Liquid Intelligence) after which the o/heating was worse. I had the radiator cleaned out and the 'top' tank was half full of muck. I am now collecting small amounts of muck in a stocking in the top hose.
    My priority now is to get the thing to idle so that I can do longer tests!
    Don
    Quote Originally Posted by David S View Post
    Don't drive a DS during a heatwave???

    It should creep forward a little at idle, but should not stall when you stop. So, you might need to look at the adjustment of the clutch engagement. There's a specific process to follow. Or the carby ... or maybe it was simply the heat?

    How have you determined that all the parts of the cooling system are OK? It's fairly basic, so it will be something like a failed thermostat, blocked radiator or bypass hose or a water pump with a corroded impeller. If I remember correctly, you had an additional cooling fan. Does it operate correctly and in the correct direction? Does it make any difference?

    What sort of coolant are you using? If you use too little water, the capacity of the coolant to cool is greatly diminished. That is why waterless coolants need other tricks to work. Perhaps, drain it and try it on straight water as a test to see whether the coolant could be part of the problem. Maybe, descale the system? Straight water is the ideal coolant, but obviously has a corrosion problem and can't be used as such.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

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    Quote Originally Posted by citroenut View Post
    Your symptoms would suggest to me that what ever you have disturbed during your cooling system overhaul has affected the relationship between the normal idle circuit & the brake controlled accelerated idle valve. I am thinking that previously too much idle air was being sourced through the accelerated idle valve.
    Check this by closing off the accelerate idle valve completely and setting the idle with the butterfly before resetting the valve for the extra 50 rpm with foot off the brake.
    If your car is injected, check that the idle circuit hasn't carboned up by removing the large idle adjust screw & running a smokers pipe cleaner through the ports.
    If your car is carburettor, has the manifold drain tube under the carburettor been blocked accidentally & the accelerated idle valve been adjusted to compensate.
    Is it possible that the throttle cable was not seating properly before & is now accidentally sitting correctly allowing the throttle to close properly ?
    A manifold air leak accidentally cured during your cooling system repairs is another avenue to investigate.

    Just a few ideas that I hope may help.

    Keep having fun.

    Richard
    Thanks for the ideas Richard.
    I will try closing off the accelerated idle valve as suggested but did you really mean only an extra 50rpm? I thought that the difference is much more than that.
    I don't recall seeing a manifold drain tube and it is quite possible that it is not open. I will I will check the throttle cable. I have never been able to get the accelerated idle speed below about an indicated 1100 rpm, probably because the throttle spindles are a bit worn. (rebushing is on the plans) It will now not idle below about 1200rpm but otherwise drives normally.
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

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    Why do you think it's overheating? Does it boil or do you have a temperature gauge that shows it's running hot? Is it dumping the coolant?

    Do you mean the remote header tank or the top tank of the radiator? Being a DS, it should have a crossflow radiator, so I guess you mean the remote header tank. If it has the header tank in the top if the radiator, it's not the correct part, although it should not overheat with it. Anyway, if it had a lot of debris in the top tank, then there could still be more in the block. Products like Stop Leak can accumulate in the block sometimes and cause blockages. Did you flush or bypass the heater matrix? It will probably hold a lot of debris.

    I assume it has a Weber carby. When people try to fiddle with the idle speed, they often change the slow running butterfly position in error. You need to check and adjust the carby from scratch, per the manual, to ensure it operates as intended. It can make a substantial difference.

    What about the ignition timing? Offhand, I recall there was a change in the flywheel peg point around 1971-ish and the difference was something like 10 degrees.

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    Hi Tresbon2, those idle speeds are dramatically excessive. From memory, normal idle should around 725 rpm, & 675 rpm with foot on brake. The clutch engagement should be adjusted so that the car barely trying to creep at 725 rpm, & the crank handle inserted should be turning. Foot on brake & crank handle should stop. There is a + & - tolerance & to achieve proper engagement & disengagement in practice you may need increase the difference in idles by as much as 75 rpm.
    I think in the archives there are files on setting up the carburettor butterflies correctly & this is absolutely critical for the correct , smooth functioning of the entire system.
    Unless the clutch fork clearance, governor engagement speed, & carburettor functions are all adjusted correctly, the car will be a frustrating pig to drive, especially in traffic.
    Please remember that the speeds I have suggested are from memory, but if wrong, they won't be out by much.
    Please try to find the postings on the correct setup, & there is no way you will get it right if the carburettor is badly worn.
    I do hope you succeed with it, because they are an absolute joy to drive when properly adjusted.

    Cheers,
    Richard

    I agree 100% with David S' comments that the ignition timing must be correct. If it is substantially over advanced , that would also hamper your attempts to get the idle speed down, apart from other harmful effects.
    Last edited by citroenut; 15th January 2014 at 09:03 PM. Reason: Added thought.

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    Quote Originally Posted by David S View Post
    Why do you think it's overheating? Does it boil or do you have a temperature gauge that shows it's running hot? Is it dumping the coolant?

    Do you mean the remote header tank or the top tank of the radiator? Being a DS, it should have a crossflow radiator, so I guess you mean the remote header tank. If it has the header tank in the top if the radiator, it's not the correct part, although it should not overheat with it. Anyway, if it had a lot of debris in the top tank, then there could still be more in the block. Products like Stop Leak can accumulate in the block sometimes and cause blockages. Did you flush or bypass the heater matrix? It will probably hold a lot of debris.

    I assume it has a Weber carby. When people try to fiddle with the idle speed, they often change the slow running butterfly position in error. You need to check and adjust the carby from scratch, per the manual, to ensure it operates as intended. It can make a substantial difference.

    What about the ignition timing? Offhand, I recall there was a change in the flywheel peg point around 1971-ish and the difference was something like 10 degrees.
    It has a temp gauge which regularly shows 100 to 110 going up long hills. The temp warning light comes on around an indicated 100 degrees. It has only boiled once, after someone told me that they fixed the o/heating of their D by adding a spoiler under the air intake so I tried that - and it was worse. It has a crossflow radiator & header tank. They took the radiator tank off. I did open the the heater system when flushing until the water ran clear. It has Repco coolant in the system now.
    I adjusted the Weber many times, by the book, and only by increasing the correct idle speed could I get it to idle. I know that it is too high and I intend to get the throttle spindles bushed but the engine & BVH were operating perfectly until yesterday.

    Ignition timing has been checked and rechecked and advanced to the point that it will just start to ping under extreme conditions.
    The W/S manual Fault diagnosis section suggests a problem could be due to a Choked Exhaust System (how do you check that?) or Incorrect valve timing. Everything else listed I have eliminated.

    thanks again for your interest, Don
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

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    Quote Originally Posted by citroenut View Post
    Hi Tresbon2, those idle speeds are dramatically excessive. From memory, normal idle should around 725 rpm, & 675 rpm with foot on brake. The clutch engagement should be adjusted so that the car barely trying to creep at 725 rpm, & the crank handle inserted should be turning. Foot on brake & crank handle should stop. There is a + & - tolerance & to achieve proper engagement & disengagement in practice you may need increase the difference in idles by as much as 75 rpm.
    I think in the archives there are files on setting up the carburettor butterflies correctly & this is absolutely critical for the correct , smooth functioning of the entire system.
    Unless the clutch fork clearance, governor engagement speed, & carburettor functions are all adjusted correctly, the car will be a frustrating pig to drive, especially in traffic.
    Please remember that the speeds I have suggested are from memory, but if wrong, they won't be out by much.
    Please try to find the postings on the correct setup, & there is no way you will get it right if the carburettor is badly worn.
    I do hope you succeed with it, because they are an absolute joy to drive when properly adjusted.

    Cheers,
    Richard

    I agree 100% with David S' comments that the ignition timing must be correct. If it is substantially over advanced , that would also hamper your attempts to get the idle speed down, apart from other harmful effects.
    My W/S manual says that the idling speed for BVH cars (presumably without brakes on) should be 850 to 900rpm but I can't get it below about 1100. I know that I need to get the throttle spindles bushed (Soon!) but the fact remains that until yesterday it was operating extremely well (except for the o/heating)

    It is possible that the timing is now over-advanced, as I advanced it to the max a few months ago. It will just start to ping under extreme conditions e.g. steep hill and 100+ temp.

    It seems to me that I must have accidentally altered something when taking the radiator out and reinstalling it or, it is a co-incidence.
    thanks again for your ideas, Don
    Citroen DS21 Pallas 1970 Renault 16TS 1976 Renault 5TS 1981

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    Sorry if any of this seems repetitive or too basic:
    Are you sure there are no air leaks between the carb and engine? Manifold gaskets? Warped carby base?
    Is that a premixed Repco coolant or what ratio of water to coolant concentrate?
    Is the distributor advance working?
    Have you ever checked the cylinder compressions?
    Have you cleaned the air filter thoroughly in petrol and added some new oil?
    Cleaned the gauze filter for the breather under the rubber elbow in carb cleaner?
    Correct plugs and leads?
    Short of resetting the valve timing, you could remove the rocker cover and a spark plug and observe the angle at which the valves open and close as you turn it over. A thin rod inserted into the piston would reveal TDC and then work from there to see if the timing is correct. Clearances correct?
    If the exhaust was choked, you probably would not have the high idle. Hard to check unless you disconnect it and try blowing air through it or actually measure the pressure drop.
    Did you dismantle and clean the carby as part of the programme of adjustments? It can accumulate a lot of rubbish and the float valve can wear out of round and leak.

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    Quote Originally Posted by David S View Post
    Sorry if any of this seems repetitive or too basic:
    Are you sure there are no air leaks between the carb and engine? Manifold gaskets? Warped carby base?
    Is that a premixed Repco coolant or what ratio of water to coolant concentrate?
    Is the distributor advance working?
    Have you ever checked the cylinder compressions?
    Have you cleaned the air filter thoroughly in petrol and added some new oil?
    Cleaned the gauze filter for the breather under the rubber elbow in carb cleaner?
    Correct plugs and leads?
    Short of resetting the valve timing, you could remove the rocker cover and a spark plug and observe the angle at which the valves open and close as you turn it over. A thin rod inserted into the piston would reveal TDC and then work from there to see if the timing is correct. Clearances correct?
    If the exhaust was choked, you probably would not have the high idle. Hard to check unless you disconnect it and try blowing air through it or actually measure the pressure drop.
    Did you dismantle and clean the carby as part of the programme of adjustments? It can accumulate a lot of rubbish and the float valve can wear out of round and leak.
    I have not checked for airleaks between the manifold and head but did repair a warped carby base. The carby was thoroughly cleaned and all jets checked for correct sizing. Mix ratio is 1/3 coolant to 2/3 water. Plugs, leads and distributor cap have been replaced. Air cleaner was serviced & compressions taken - all dead even but a little low. Tappet clearances were/are to specification.

    My dilemma is that the car has been running well, apart from the hot-running, for some time and suddenly it wont idle yet runs well above idle speeds. I was quite sure it had to have a blocked idling jet but they were clear.

    Don
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    Silly questions, but...

    Have you at any time replaced the thermostat?
    Is the thermostat installed the right way around?
    Have you tested the existing thermostat for operation in a saucepan of water being brought to boiling? (ensure you use the best pan in the kitchen to attract maximum attention to this important task)
    Craig K
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    Not a silly question, Craig. I tested the thermostat recently simply by pouring boiling water on it. I think a better check is in order. Maybe I should do a test without it. The heater may not work well then but it's hardly needed at the moment! Is it possible to put it in upside down? I will check that too.

    Thanks for your help, Don
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    Quote Originally Posted by tresbon2 View Post
    Not a silly question, Craig. I tested the thermostat recently simply by pouring boiling water on it. I think a better check is in order. Maybe I should do a test without it. The heater may not work well then but it's hardly needed at the moment! Is it possible to put it in upside down? I will check that too.

    Thanks for your help, Don
    Yes it is possible to install USD. I can't remember which way is correct at present but someone else will know.
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    Quote Originally Posted by tresbon2 View Post
    I have not checked for airleaks between the manifold and head but did repair a warped carby base. The carby was thoroughly cleaned and all jets checked for correct sizing. Mix ratio is 1/3 coolant to 2/3 water. Plugs, leads and distributor cap have been replaced. Air cleaner was serviced & compressions taken - all dead even but a little low. Tappet clearances were/are to specification.

    My dilemma is that the car has been running well, apart from the hot-running, for some time and suddenly it wont idle yet runs well above idle speeds. I was quite sure it had to have a blocked idling jet but they were clear.

    Don
    Don,

    With a carburated 71 BVH the low idle speed is typically set between 825 to 875 rpm. The 'high idle' is adjusted with the aux. air bleed screw to 250 rpm above the low idle setting. The 'idle' jet on those Webers is the low speed or secondary jet on the secondary throttle. If the carb has been taken apart/cleaned and the primary throttle plate not set using a feeler gage that could well be the source of the problem. The primary throttle plate adjustment screw has a lock nut on it for a reason. Correctly let one should just be able to slide a 0.005" feeler gage between that throttle and the carbs venturi.

    Secondly all idle speed adjustments are made using the secondary throttle plate. And these adjustments need to be done with the engine at normal operating temperature - not the temperature one gets after starting the car and letting it idle for 5 minutes.

    The problem you are experiencing could also be due to either a 'scored' or partially clog idle mixture jet. From personal experience I can assure you that having the idle mixture screw 1/4 to 1/3 turn too lean will cause the problem you are experiencing. Additionally that idle mixture screw should be between 2 to 3 turns from fully seated. If less or more it means either gas leakage via the main circuits or excess air getting into the the air flow.

    Steve

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    Quote Originally Posted by UFO View Post
    Yes it is possible to install USD. I can't remember which way is correct at present but someone else will know.
    I have looked at the diagram in the W/S manual and confirmed that mine is in the right way up.

    Don
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    Check to be sure the carb has not come loose on the intake manifold. That will cause your idle problem.
    As to overheating, check to be sure that all 4 front brake pads can be wiggled in the calipers. Sticky brake pistons will cause overheating.

    Via the aussiefrogs App

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    Hi Steve, thanks for your ideas.
    When I had an idling problem a year or more back I got Adelaide's DS 'expert' to have a go at it. I was horrified to see him attack the primary throttle stop screw and not surprised when he did not fix the problem. I then had to redo the setting, and eventually got the idling OK, albeit a bit faster than the book says. I am confident that the throttle plate setting is now correct.
    When our weather gets cooler on the weekend (it is 46C in my shed at the moment) I will check the idle mixture adjustment.
    Do you think that somewhat worn throttle shafts could be part of the problem?
    My W/S manual says that the low idle speed should be 625-675rpm and the accelerated speed 850-900.

    Don
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    Don,

    I know the W/S manual gives those aim points. Can tell you from long experience with a 21 BVH in the Los Angeles area that those figures can be low in hotter than normal conditions .

    1) Worn throttle shafts will not cause the problem. Almost always the one the wears to a sufficient point to cause any problems is the primary throttle shaft. When that happens one tends to get a 'hunting' idle point.

    2) The low speed jet on the primary throttle (facing the engine) has no effect on idle mixture. What you do need to check is the condition and size of the actual 'idle' jet that is screwed into the secondary idle. Normally that is 0.70mm jet (stamped on the side in really small numbers) for BVM/BVH cars. Borg Warner equipped cars has a 075mm jet. What you need to check is that the jet is undamaged and that the calibrated hole is round without any 'burs'.

    3) Actual idle 'mixture' is more critical with a BVH than a BVM. And, depending on engine condition, may have to set just a tad on the rich side compared to a BVH car. The difference, typically, is less than a 1/4 turn of the idle mixture screw. This is more of a problem in hot areas as the incoming air is 'thinner' than when cooler.

    4) However, if the car is running really hot no matter what you do the problem may still be there depending on how hard you come to a stop. Look at some of the info from other threads on over-heating and see if the suggestions given might be applicable to your situation. Also make sure (some one else may have already mentioned this) that the Nylon drain tube that is attached to a nipple on the bottom of the intake manifold is there and secure, and of the correct length - should be 400mm.

    There is on last thing to check - and it is simple. There is a little hose connection screwed into the intake manifold just below the base of the carb. There should be a small rubber hose running from Nylon 'T' that connects the lower and upper crank case breather hoses to the intake air hose that runs from the air cleaner to the top of the carb. Unscrew it and ensure that the calibrated orifice is not plugged with carbon. If it is carefully clean it out. Ones that are plugged can cause idle setting problems.

    Steve

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    Quote Originally Posted by daffyduck View Post
    Check to be sure the carb has not come loose on the intake manifold. That will cause your idle problem.
    As to overheating, check to be sure that all 4 front brake pads can be wiggled in the calipers. Sticky brake pistons will cause overheating.

    Via the aussiefrogs App
    The carb nuts were a bit loose and I have tightened 3 of them. Still trying to find a way to tighten the front one adjacent the rocker cover with out removing the cover.
    All brake pads can be wiggled.
    Thanks for that, Don
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    Quote Originally Posted by Citroenfan View Post
    Don,

    I know the W/S manual gives those aim points. Can tell you from long experience with a 21 BVH in the Los Angeles area that those figures can be low in hotter than normal conditions .

    1) Worn throttle shafts will not cause the problem. Almost always the one the wears to a sufficient point to cause any problems is the primary throttle shaft. When that happens one tends to get a 'hunting' idle point.

    2) The low speed jet on the primary throttle (facing the engine) has no effect on idle mixture. What you do need to check is the condition and size of the actual 'idle' jet that is screwed into the secondary idle. Normally that is 0.70mm jet (stamped on the side in really small numbers) for BVM/BVH cars. Borg Warner equipped cars has a 075mm jet. What you need to check is that the jet is undamaged and that the calibrated hole is round without any 'burs'.

    3) Actual idle 'mixture' is more critical with a BVH than a BVM. And, depending on engine condition, may have to set just a tad on the rich side compared to a BVH car. The difference, typically, is less than a 1/4 turn of the idle mixture screw. This is more of a problem in hot areas as the incoming air is 'thinner' than when cooler.

    4) However, if the car is running really hot no matter what you do the problem may still be there depending on how hard you come to a stop. Look at some of the info from other threads on over-heating and see if the suggestions given might be applicable to your situation. Also make sure (some one else may have already mentioned this) that the Nylon drain tube that is attached to a nipple on the bottom of the intake manifold is there and secure, and of the correct length - should be 400mm.

    There is on last thing to check - and it is simple. There is a little hose connection screwed into the intake manifold just below the base of the carb. There should be a small rubber hose running from Nylon 'T' that connects the lower and upper crank case breather hoses to the intake air hose that runs from the air cleaner to the top of the carb. Unscrew it and ensure that the calibrated orifice is not plugged with carbon. If it is carefully clean it out. Ones that are plugged can cause idle setting problems.

    Steve
    I have been tinkering with adjustments since my last report. Once again I could not get the responses to the various adjusting screws that the manual states. Even with the secondary throttle stop screwed right out I can not get the normal idle speed below1100rpm. However under brakes the rpm drops to about 750 and the engine does not stall now.
    Being reasonably happy about that I just took a trip up the hill and along the freeway and, wonder of wonders the cooling system finally behaved itself. Max temp seen, at the top of a long steep climb, was 90C compared to 110 before and normal running sees around 80.
    So on both counts I am much happier now. Even the brakes don't snatch now, due to my patent modification - a piece of an aluminium soft drink can fastened underneath the steering column rotating joint, so that the leaking LHM does not end up on the RHS brake caliper. (Its a RH drive car of course) A proper repair is on the TO DO list!
    My next task is to check that drain tube (I certainly don't remember seeing one) and the calibrated orifice.

    I really appreciate all the advice you so freely make available, and all the other Aussiefroggers too.

    Don
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    From your last posting it seems the accelerated idle valve is suspect. If the idle speed drops from 1,100 to 750 when the brake is applied, surely the excess air is coming through that valve in some way ? I am unfamiliar with its internal construction, but I would be looking to see how that could happen. Is it's gasket leaking or missing ? Is an 'O' ring tired or missing ? Is there some porosity or corrosion allowing air to leak when the valve is open ?
    Just some ideas .

    Richard

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    Don,

    That you get no reaction from the either the secondary throttle set or the mixture indicates that either there is a good sized air leak somewhere or excess gas is getting into the intake. To try and track down the problem area do two things. 1) With the engine idling turn in the accelerated idle aux. air bleed screw (the big brass knob) until fully seated. Idle should drop to the low idle speed you noted when applying the brakes. If it does then 2) Gently seat the idle mixture screw counting turns (full and fraction). Did this 'kill' the engine. If so then you do not have excess gas getting into the intake from an area of the carb it should not be issuing from. FYI, typically having the idle mixture screw less than one full turn from fully seated will kill a normal set up. If the engine will still run with the mixture screw fully seated means you have gas getting to the intake from another carb circuit.

    If that is the case you really should remove the unit and go though a proper set up of the carb. Otherwise you are going to be chasing your hind end trying to get things sorted out.

    When setting up the carb you should have the accelerated idle air bleed screw fully closed or seated. You then set up the low idle speed with the secondary throttle set screw in combination with the idle mixture screw. As I mentioned before the idle mixture screw will typically be between 2 to 3 turns from fully seated (closed) when the engine is at the proper low idle speed. Then the high idle is set with just the aux. air bleed screw. Nothing else is touched.


    Richard - his system is working as intended. With a BVH releasing the brakes allows more air via the accelerated idle passage in the carb to increase idle speed. System design is trying to emulate how one drives a manual car. As idle speed increases the centrifugal regulator is set so that clutch piston pressure is released to just bring the clutch disk and flywheel just into contact. IOW the car will just begin to creep with no use of the accelerator. There is no 0-ring in that unit. Brake system pressure (from the LHS front brake caliper) closes off the aux. air passage and drops the carb to its low idle setting. Releasing the brakes allows a small spring in the aux. idle device to push the piston back opening up the air passage way and the idle goes to the accelerated idle speed that is set with aux. bleed screw.

    Correction - In my last post I mistyped BVH when I meant BVM - BVH cars typically need a bit more enrichment of the idle mixture compared to BVM cars - not the other way round .

    Steve

  25. #25
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    Citroenfan, I am aware of the basics, but not specifically of the accelerated idle valve internals on a carburettor, as both my BVH cars were injected.
    I still don't see why if, with the valve closed idle speed drops to 750 rpm, then opening the valve to achieve an extra 75 -100 rpm should be possible instead of the 1,100 rpm as now ?
    Perhaps the carburettor has been setup with the accelerated valve open, instead of closed as you suggest.

    Cheers,
    Richard

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