Weber Idle Adjustment Problem - Page 5 - Alfa Romeo Bulletin Board & Forums
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post #61 of 76 (permalink) Old 03-05-2019, 04:29 AM
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Hi Giacomo,


You probably know all this already but I tell you this from my own experience and only for helping you.
For finding an error, only change just one parameter at a time and measure again. for example, just change one mixing screw and measure, keeping the pipes of the measuring device untouched. Keep also in mind how your measuring device was attached if you have disconected it. Are the tubes numbered to avoid mistakes?
Are the little metal pipes at the end of the tubes, that go on the carbs, screwing and closing correctly?
My next step would be therefor to check as good as possible the mercure device by changing the plastic pipes from their places on the carbs again and again untill you have had all the possibilities , noting down and comparing each time those results to be sure your device works correctly.
Have you changed the position of the carbs yet ? If you would do this, don't change anything else on the carbs at that moment otherwise the readings can mislead you.
This are just some thoughts I had when reading the posts of this thread.
Just hope to be of some help,
Rgds,
Thierry
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post #62 of 76 (permalink) Old 03-05-2019, 05:11 AM
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Thierry
you are completely right. In fact, I tried to change one parameter at a time. First of all I checked the compression and the play of the valves even if the engine only has 4000 km. Then I made sure that the carburetor supports did not vacuum air, I replaced them.
I tried to change the measurement tool, nothing happened.
I tried to clean the carburetors and the jets, nothing happened
I tried to reverse the jets, nothing happened.
I tried to reverse the mixing screws, nothing happened.
I tried to replace the bearings, something changed.
the next step will be to replace the mixing screws with others of different types.

one step at a time I want to try to solve this problem without haste. I certainly do not take it to the mechanic before I've tried them all.




Giacomo
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post #63 of 76 (permalink) Old 03-05-2019, 06:22 AM
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Salve Giacomo,

I'm sorry but I have no other ideas as those that I mentioned before for cracking this 'nut'.
I do have big appreciation for your perseverance.
I know you will be proud of yourself when having found the error by elimination like you are doing.

Meanwhile, may I tell you a little story that I still remember from when I was young:

My father was a schoolteacher of automechanics for last year students.
When they had practice lessons, they sometimes could have a problem with an engine that they couln't resolve and then they asked my father to come and help them. When they were gathered arround that specific engine, he asked for the steps they already had taken to find the problem. Then instead of giving the solution, he turned his back and walked away saying: "interesting engine".
I think he was preparing them to be better mechanics.They had to search themselves for the solution of the problem just like they would have to do once they were graduated and when working for a boss.
Maybe your engine is such an interesting one too !!
This being said, please be sure I hope you can resolve the problem quickly!

Saluti cordiali,
Thierry
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post #64 of 76 (permalink) Old 03-05-2019, 06:47 AM
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I could take all your advice and go away and instead I decided to continue and share my experience, also because I know, some of you do not sleep at night to know how this story ends
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post #65 of 76 (permalink) Old 03-05-2019, 07:43 AM
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It is likely that since change was noted when the bearings were replaced that the removal and replacement of the butterfly plates was actually the cause of the change. In my experience, there is normally more air leakage past the center bronze bushings then from the outer shaft ball bearings with NEW Webers. Generally it is not advised to remove and replace worn-in butterfly plates or shafts for removal and replacement of bearings. The seal on the ball bearings is a wear/ replacement item.
Normal procedure involves exposing access to the bearings, cleaning them in place, repacking with waterproof grease, a new leather oil soaked seal, seal retaining spring, and spring retainer. Sealed bearings are difficult to impossible to properly clean in place and are not recommended for Webers that used unsealed bearings, due to the necessity of removal and replacement rather than cleaning.
All that aside, butterfly plates and aluminum throttle bores wear in with use. Removal and reinstallation of the plates WILL change manometer readings do only to changes in the plates new sealing position. Often it is very difficult to impossible to re-set used and sometimes new plates in worn throttle bores so air leakage is the SAME between throats.
Minimally 50% of the Webers that appear in my shop with re-set butterfly plates have those plates correctly sealing the 2 throttle bores in any given body. Another 10% or so have damaged butterfly bars, either spread slots or twisted, from removal with a drift rather than the correct slide puller.
For all the reasons above it is not suggested a shop or individual unfamiliar with Weber service remove bars and plates for bearing cleaning.
I believe if you want to see more changes in manometer readings, you need look no further than butterfly plate positioning and throat seal.
All the above is only from 50+ years experiences in Weber service.


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post #66 of 76 (permalink) Old 03-21-2019, 12:14 PM
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Thank you for sharing your great experience

the old bearings were noisy but there is also to say that those bearings, in my opinion, are not subjected to a great rotation job. I tried to install the new mixing screws being very careful and I must say that the old mixing screws are safer because they have that step that blocks them when they are closed completely. So they used them again.
It is not easy to always understand what I am told because even using a translator it is not always easy to understand what it translates. But now reading and rereading I understood what you mean.
Alignment of the vacuum gauge in the single carburettor is not due to the mixing screw but to the installation position of the throttles.


if you wanted to replace butterflies with new ones, would you recommend replacing the butterfly fixing screws?
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post #67 of 76 (permalink) Old 03-21-2019, 03:05 PM
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You will probably run into more difficulty with "new" butterfly plates. There are 2 basic variants, 78 degrees, and probably on your 32's, 79 degrees, 30 minutes. These DO NOT INTERCHANGE! Further, the aluminum throat bores are now worn-in from the old plates. Installing new, correct angle plates, would not seal worn bores.
This is the big reason why removal and replacement of plates and bearings is not a good idea unless you are very good at resetting plates so leakage is the same on BOTH bores of any DCOE. I reset a LOT of plates, on worn bore Webers needing new butterfly bars or with a questionable bearing. I've done this for 50+ years, and still, getting some correct, one bore to match another, with worn bores, can take a very long time, as well as requiring a large supply of used plates.
If they are incorrect now, new correct angle plates will still require some skill to correct the balance problems between worn throats in a DCOE body, and new plates may make the leakage (balance) actually worse.
There is no simple or easy solution.


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post #68 of 76 (permalink) Old 03-30-2019, 09:14 AM
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Dear Gordon
Thank you very much for your reply, always too kind.
I've thought so much about what to do. In the end I decided to remove the carburetors again, remove the butterflies and see the conditions more accurately.






I did not like those steps (wear) and those signs of those who intervened before me.
I bought butterflies and screws that hold new butterflies. I will try and update you when I mount them.
In the end maybe I'll understand that I had to take them to review by those with experience and skills like you, but I would have enjoyed it at least a little!
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post #69 of 76 (permalink) Old 03-30-2019, 02:27 PM
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You can easily see part of your problem, the rounded edges on the angle cut plates. The edges once were sharp, as the plates from a 45DCOE pictured below. These will be used to replace damaged plates on the 45DCOE's and are used. They do show some wear on the edges where the bar passes over them which is the first area to wear. You can see this in photo #2 and #3 below.
For this replacement, the existing plates show the same amount of wear, new with old replacements does not work as well as when they are matched. The bigger problem with your plates with the rounded edges may (or may not) be the seating surface in the throats, that may have close to invisible wear rings cut in the throats. However, if you can get both plates in each body to leak very close to the same amount, the balance link between bodies will balance one to the other.
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Last edited by Gordon Raymond; 03-30-2019 at 02:29 PM. Reason: spelling
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post #70 of 76 (permalink) Old 04-03-2019, 01:13 PM
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Ciao

I have news

I got the new screws and the new butterflies. The difference I found is that the new ones are totally round, at least so it seems to me, while the old ones in the side points were straight. unfortunately I have no photos but these are:https://www.ebay.it/itm/2x-Valvole-a...72.m2749.l2649

eccole installate:


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post #71 of 76 (permalink) Old 04-03-2019, 01:23 PM
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They adapted easily and I tried to center them as best as possible. But I couldn't do miracles.







you have to take into account that they are photos and therefore the position of the objective of the phone can be misleading.
But with the benefit of hindsight I must say that the result is positive, at least for what I expected.




from the left the number 1 on the right the number 4. However the carburetors have the same values ​​or almost, in the sense that the body of left of each carburetor is high while that of right is lower. I do not know if it is right that this is so, the number 4 is perhaps lower due to the servobrake, I do not know I must try to exclude it
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post #72 of 76 (permalink) Old 04-03-2019, 01:44 PM
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If these are on an Alfa, the balance link between the Webers is the adjustment needed to correct front Weber-rear Weber imbalance.


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post #73 of 76 (permalink) Old 04-03-2019, 01:59 PM
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It's too much if I ask you how to adjust the balance between front and rear
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post #74 of 76 (permalink) Old 04-03-2019, 03:29 PM
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The linkage pictured below. It needs to be disconnected at the ball from the throttle linkage, so that only the butterfly plate return springs effect plate position. The round head slotted screw is the IDLE SPEED adjustment screw, the hex head slotted bolt on the center linkage is the front / rear balance screw.
Play with both engine idling to see which one does what, Idle SPEED should be 800-1100 rpm, and balance set to get your manometer readings similar, front to rear Weber.
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Last edited by Gordon Raymond; 04-03-2019 at 03:30 PM. Reason: spelling
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post #75 of 76 (permalink) Old 04-03-2019, 04:22 PM
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Grazie
Thanks Gordon I thought you were talking about some adjustment that I had not yet discovered, thanks again for the explanation is already an operation that I did as you described.😁
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