Why does Bing suck so badly

How do I adjust my Bing carburetor on the BMW?
- (C) R. Restat / 2004
First we differentiate between the following:

a) were the carburettors disassembled? E.g. after cleaning or general overhaul, then you run through the "big program"


b) the "small" one, ie idling and synchronization.

We'll start from scratch.

To do this, we first have to make the basic setting

First turn the idle mixture screw all the way in and approx. a Turn out again.
(I.e. turn the slot of the screw a little more than 360 degrees)

Unscrew the throttle valve stop screw all the way. Then place a piece of paper between the screws and the stop and turn the screw in until the paper can just be pulled out without being destroyed.

With a little practice you can do it. If necessary, ask a smoker who turns himself. He always has paper with him! But with confidence: Newsprint is also possible.
Now the throttle valve stop screw a half Turn further.
(I.e. turn the slot of the screw 180 degrees)

Three quarters might also be good, it depends a bit on the type.

With this basic setting, the engine usually runs very well. You can now decide whether you want to set the synchronization while standing by ear or with vacuum clocks. In any case, it is not without the clocks.
But hearing is not really accurate!

If the engine starts up on its own, the throttle valves are open too far. I.e. the stop screw was screwed in too far. Then the engine sucks in too much air and lifts the vacuum piston (part no. 13) and "accelerates itself".

After you have set the mixture screw and throttle valve nicely, now comes a proper test drive. Why? ok, the engine has to be warm for the next procedure! I say about 20km or a little more!

If you are satisfied, then everything is fine! Otherwise?

Yes otherwise we continue here ... so part b)

The idle

We only continue at idle.
And that's exactly why the engine has to be warm, not necessarily for the synchronization, it's more about vacuum.

So, here too there are the best methods. Basically always the same. You have to carefully screw the mixture screw by 1/8, max. 1/4 back and forth until the idle gas has, so to speak, its "highest level". So before it goes down again neither in one nor in the other direction. So find the golden mean somewhere.

The very clever ones paralyze a cylinder. Maybe they don't hear so well anymore.

But if you don't pull it off with the spark plug connector as in B.'s repair instructions!
Modern electronic ignition does not always tolerate this. This does not matter with older contact ignitions.
So now the cylinder is paralyzed by pulling out a candle cap, inserting another candle that you put on the cylinder. lays. So you can adjust one cylinder (namely now the other) in peace.
And vice versa. (ok, if you like it ...) It works even if both are running.

Perhaps another tip on the side: If the engine bubbled a little badly when taking off the accelerator or reports a slight "slap", this indicates a so-called "skinny slap". In this case, turn the or both mixture screws a little bit out (max. 1/8 turn)

If that's ok, the throttle valve and trains come on.


Oh, we still need a measuring device. Either vacuum clocks (great, accurate and expensive) or
a U-tube manometer (simple, not that accurate but cheap). Such a simple oil-filled U-tube sure does the job for most.

I'll explain how to build this later.

Now it is set for the time being.
We now take the measuring device and now adjust the pressure equilibrium on the left and right by screwing the throttle valve stop screws very carefully in / out a little.
And make sure that the cables have enough play (4-5 mm) to adjust. (So ​​strictly speaking the sleeve is meant, well you know)

When that is resolved, we allow the engine to cool down briefly. OUT!
Now on again ...

With the help of the manometer we now adjust the pulls. To do this, loosen the lock nut slightly and carefully turn the cup a little. (The cable play can now be reduced to just under 1mm, provided that the throttle grip has enough play. If necessary, readjust above)
And in this way:
if the pressure on the display goes down, the flap is open too far compared to the other, pull in a little. Otherwise the other way around. It is recommended to follow the "slower" cylinder, otherwise the trains or the train may become too tight.
Ok, when that's done, fix everything again and it's good.

And don't be too specific. ok, ok, I know there are specialists who can set the pressure difference to 0.001 bar, some even with mercury columns or with Colortune and whatever!

Incidentally, a good carburetor setting naturally assumes that all components such as springs, membranes and nozzles are in working order. In addition, the valves and ignition timing must be set correctly.

I should also mention that a liquid column difference of approximately 10 cm corresponds to 10 mbar.
(only correct for water and not for oil, but roughly)
If you get hired, then you're fine.
With a little patience, the throttle valve stops can be adjusted so that the two columns have the same level. I.e. about 1/8 turn of the stop screw.
That means approx. 1-3 mbar pressure difference.

This is more difficult with the rope hoists. I think you can do quite well with a tolerance of 3-8 mbar (or cm level).

So a little care, but don't overdo it! Also depends partly on the quality (age) of the trains and the type of laying.

The final test drive is important - if only because of the fun factor!

After an extensive test drive, you can also see from the candlestick picture whether you have done everything correctly.
Which, admittedly, is becoming more and more difficult with modern fuel.

And the tingling sensation in the footrests is suddenly gone!

I mean, a badly synchronized motor vibrates and you can tell.

Have fun and, as always, all information without guarantee (performance) !!!!

U-tube self-made. 4m hose, the vertical one (the board) between 1.2m and 1.5m.
Filled to 1/3 the height with engine oil. (You can still experiment here!) Other liquids and thus viscosities, e.g. fork oil or wheel gloss (is beautiful red). Or with vibration dampers, i.e. push a piece of hose with a smaller diameter into the bottom of the U (exactly in the middle), etc., etc.
That is certainly not the culmination of apparatus engineering, but it is very helpful and in most cases accurate enough.

Oh yes, I once read somewhere that someone "synchronizes" the trains as follows:
Dismantle the carburetor and place the cylinder side on a cardboard box or similar. lay. Let a ball roll in from behind from a ball bearing (as large as possible).
Then turn the throttle and see / hear which ball falls out first, readjust, etc.
Nice idea...

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And next time I'll explain to you what the springs in the valve piston are good for.