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Thread: Adjusting Linkages to Idle stop verse WOT stop

  1. #1
    Registered User jedwards's Avatar
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    Adjusting Linkages to Idle stop verse WOT stop

    Gentlemen,
    I "appear" to have resolved by manifold vaccum leak at last, and are now moving onto the Weber Linkages, a subject well covered in this excellent Forum.
    However, I am having trouble achieving carburettor sync at Idle and at WOT stops, as I believe is a very common problem, if not a the standard.

    I have read the extensive discussions regarding why this problem exists with Webers, however I have struggled to find out what I can do about it and what the solution is.

    This is my problem.
    I have a nasty hesitation under load that did not go away with the vacuum leak, as I had hoped.
    This is a leaning out situation, which can be corrected by pulling the choke out half way.

    So I adjusted the linkages so both webers hit the WOT stop at the same time. This required #1 rod to be lengthened my a few mm. However now I cannot get both to hit the idle stop at the same time. The differcne in rod length holds #2 carbie off idle, making the car idle too fast and unbalancing the carbs. This thtows out the progression hole alignment and in terun mucks up that.

    I seem to have a few options I have not tried yet.

    Option 1 - increase the idel and mains jets as Jim suggested in one of this posts.
    Option 2 - create English long holes in the horizontal control arm supports, then sets the lenghts of the rods to acheive Idel stop sync. How, see how much out the WOT stop syn and accommodate that by raising or lowering the control arm at one end until both carbies sync at WOT witout adjusting either rod's length. Probably requires a aweful lot of trial and eror, but not sure what else is available to me.


    Any thoughts?
    best wishes
    Jeff

  2. #2
    Administrator wpuryear's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    In my experience the most common cause of hesitation or even complete stalling is accelerator pumps not injecting immediately on pedal movement or from insufficient quantity. Poorly synchronized carburetors generally shows up as a vibration or a droning engine due the difference in power from the pairs of pistons or in the extreme, very rough running.

    Walt

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    Administrator JimVillers's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Jeff .... An out of sync at wide open throttle is not much of an issue as it is normally small. Your hesitation is your jetting or other carburetor problems. If you have the air log and do not have the club adapter, do your tuning with the air log off.
    Jim Villers
    1961 190SL, 230SL 5-speed, MGB 5-speed, Porsche 356C; 1967 Porsche 911; 1950 Jeep CJ3A

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    Administrator wpuryear's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Wouldn’t hesitation from jetting occur mostly during transition from idle to main jets so in a limited rpm/load range but injection pump issues would occur across the entire spectrum except perhaps very high rpms?

    Walt

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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Jeff, you may not have noticed but the rear carburetor sits a little higher than the front. The linkages from carb to the overhead shaft are somewhat different. I don't have Webers so listen to Jim and Walt. I set the idle speed with linkage disconnected then adjust the linkages to that.
    Jack English
    1960 #15229 Since 1972
    1971 MBZ 300SEL 6.3 Since 1983
    1999 MBZ 430E Factory Delivery

  6. #6
    Registered User jedwards's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Quote Originally Posted by JimVillers View Post
    Jeff .... An out of sync at wide open throttle is not much of an issue as it is normally small. Your hesitation is your jetting or other carburetor problems. If you have the air log and do not have the club adapter, do your tuning with the air log off.

    Hi Jim,

    I purchased the Redline K241 kit, which was supposedly set up specifically to suit our 190SLs.
    This kit provide the DCOE 40 type 151 carbs:
    According to Redline, these are jetted as:
    1.25 MAINS
    30 MM CHOKES
    .45 PUMP JETS
    2.00 AIR CORRECTORS
    0.55 F9 IDLES

    In one of yours more recetn posts, you suggested changing the Idle jets to 0.45 F8, which I have done.
    I don't known what jets were supplied in a standard K241 kit for:

    Aux venturi
    Emulsion tube
    Acceleration pump jet

    I beleive your recommendations for Emulsion tube is F2 and Acceleration pump jet is 0.54

    Any other chances I should explore, Jim?

    regards
    Jeff
    Jeff Edwards - Perth, Western Australia

    Current Garage
    1963 Mercedes 190SL
    1953 Series 1 SWB Land Rover
    2007 Mercedes SL350 (daily driver)
    2017 Audi Q3

    Previous Restorations
    1971 Porsche 911T
    1969 Mercedes 250SL Pagoda
    1967 Aston Martin DBS
    1971 BMW 2002 Cabriolet
    1932 Austin 7 Tourer

  7. #7
    Administrator JimVillers's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Jeff .... Tuning carburetors is like getting glasses; is this better or is that better. Every car is a little different and trial and error is normal.

    First, get larger pump jets; most of us use 0.55 pump jets. Main jets are normally 1.20 or 1.30 and idle jets are normally 0.46F or 0.50F. When you reach the sweet spot you car will run great.
    Jim Villers
    1961 190SL, 230SL 5-speed, MGB 5-speed, Porsche 356C; 1967 Porsche 911; 1950 Jeep CJ3A

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    Registered User tommd's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Quote Originally Posted by JimVillers View Post
    Every car is a little different and trial and error is normal. .
    Jim, I am not disputing, but I do not understand. MB sent out thousands of cars off the assembly line, all with the same jetting. I oftened wondered how oems sized carbs. How much is by charts, math, vs how much is by trial and error. They certainly did not do each engine individually.
    Tom D.
    1961 190SL

  9. #9
    Administrator wpuryear's Avatar
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    I'm not getting any rebuttal on my argument that jet sizes are not the problem but most likely accelerator pumps given the statement:

    "I have a nasty hesitation under load that did not go away with the vacuum leak, as I had hoped.
    This is a leaning out situation, which can be corrected by pulling the choke out half way."

    The surest way to diagnose the problem is with a wide band oxygen sensor.

    Ready to be proven wrong.

    Walt

  10. #10
    23K Original Miles slover's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Quote Originally Posted by tommd View Post
    Jim, I am not disputing, but I do not understand. MB sent out thousands of cars off the assembly line, all with the same jetting. I oftened wondered how oems sized carbs. How much is by charts, math, vs how much is by trial and error. They certainly did not do each engine individually.
    The big difference being manufacturers all had new engines built to the same specs. We have old engines with god knows what in some cases.
    John Lewenauer - Newsletter Editor - Regional Director
    1961 190 SL
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    Registered User tommd's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Quote Originally Posted by wpuryear View Post

    Ready to be proven wrong.

    Walt
    Prove you wrong? I doubt it! I agree with you, and more. In my opinion, this is a very "unknown" situation, and needs to be treated as such. If I remember, Jeff had just gotten is car back from a restorer, including a rebuild, or at least a going over the solexes. Because it had issues, Jeff got Weber. To my knowledge, it was never completely determined if the solex problem was carburation, and now we are on to Webers. Jeff, I have forgotten what all you have done, so I am probably repeating. But, if you are not sure, I would b checking everything. Compression, valve timing and setting, and especially ignition, dwell and timing- I do believe you have electronic ignition, so timing and good spark. Cap rotor, wires. Of course, vacuum leaks. And to jets? My limited knowledge, first is the Venturi size. Now I am out on a limb, but with all the issues that we have with Solexes, I I have some too, it seems there are even more with Webers, although some are very happy with them.
    Tom D.
    1961 190SL

  12. #12
    Registered User tommd's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Quote Originally Posted by slover View Post
    The big difference being manufacturers all had new engines built to the same specs. We have old engines with god knows what in some cases.
    John, yes, but... But typically an old engine would be worn, and in my experience, I have never felt or heard that a carb is modified for that reason. And if old means "broken" then I would spend my time and money fixing the problem, not adapting to the problem.
    Tom D.
    1961 190SL

  13. #13
    Registered User jedwards's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Hi Jim, Walt and Tom,

    Many thanks for your input and advice. I have new jets on order.

    Yes I have been through various issues, but the engine was fully rebuilt by a retired Mercedes Mechanic, who did his precentorship on these engines, so I am confident that things are as good as they can be.

    I initially struggled with the Solex, mainly due to fuel leakage. They seem to drip a lot of fuel, filling the house with petrol fumes and giving my wife migraines. It was the Solexes or the car that had to go. I chose to keep the car.

    Weber DCOE 40 type 151 solved almost all my issues and gave me a car that started immediately and ran quite well. I’ve spend countless hours on the linkages and syncs to get things even better. .

    I disliked the induction roar of the Webers so installed the original airlog and support brace, ,and that is where my recent adventures started.
    My brace must be a bit too long and it took quite a bit to get it fit, Unfortunately, the long support brace lifted the airlog and carbs, upsetting the gasket seal and introducing a very persistent vacuum leak which took me several weeks to resolve.
    Last weekend I finally resolved the vacuum leak with a Remflex gasket, new stepped washers and new nuts and higher torque than recommended by Remflex.

    Unfortunately, on the first test drive, I found I now had a major hesitation under load.
    This can be corrected by pulling the choke out OR by being supper gentle with the throttle.

    I have a new 123 electronic Distributor, an MSD multispark ignition system which all seems to work perfectly. Jets are all clean, and float levels correct fuel pressure is good.

    I will replace the pump jet and get slightly large mains, to try.

    I will report back on progress.
    regards and thansk
    jeff

  14. #14
    Administrator wpuryear's Avatar
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    You should determine if the pump is indeed injecting fuel and if not, determine why. Pump piston, check valves, nozzle, springs, linkage. Itís certainly possible itís not injectors but ďThis can be corrected by pulling the choke out OR by being super gentle with the throttleĒ are classic symptoms.

    Walt

  15. #15
    Registered User jedwards's Avatar
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    Re: Adjusting Linkages to Idle stop verse WOT stop

    Thanks Walt,
    I have the larger pump jet recommended by Jim on order.

    I beleive it is working, as I can hear the pump injecting when the engine is off and I move the linkages. A couple of pumps will fire it up nicely from cold, so it must be getting fuel from the pump.

    Can you suggest a definative way of testing the accelerator pump without removing the carbs from the engine and watching the squirt?

    regards
    Jeff

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