CB1100 Idle speed instability problem

[max]

Enzo there are 4 calibrated gauges required together with the knowledge to deal with the interaction of the iacv positions.

From the question i think you may not have done a carb/ throttle body sync before, so before changing anything i would suggest to watch several yt video's to find out what's involved, how to do it and why.
Throttle sync is only required when the engine is warm and at idle, there is no other reason to adjust the sync adjustment which is why Honda does not supply service info, they want to avoid the risk of getting it wrong which is easy to do, the adjustment screws are not fixed like the old carburettors so by adjusting too much you can drift out of range and end up with a rich or lean mixture.
With carburetors you adjust the amount of fuel mixture, with a throttle body you only adjust the amount of air per cylinder, there is a difference.

For instance when i bought my cb919 the engine sounded like a harley at idle, the engine only ran on 2 cylinders, it took me a while to work out why, and after syncing the throttlebody with the 4 gauges it started to run like it should have; somebody mis-understood what they did and got it wrong.
Once i had the vacuum gauges installed and started the engine it was very apparent that the sync was off.
All four cylinders have the same capacity so they produce the same amount of vacuum at each intake stroke at the intake when the valves open, this amount can be measured with 4 individual vacuum gauges and adjusted so they read the SAME amount of vacuum supplied through the iacv and adjusted ( equalized ) by the 4 screws under the throttle body.

As soon as the throttle is opened slightly the butterfly valves and the tps start doing their job and the idle screws are no longer of any importance, they are only required when the butterfly valves are closed.

You can then verify this by using a piezo electric pressure sensor in the exhaust and watch the pulses it produces with each exhaust stroke which should be equally the SAME, you do need an automotive oscilloscope for this check so you can record and watch the pulse train.
Hope this helps.

My advice; if there is no problem don't introduce one.
With all respect for your ability and thanks for all your help, i appreciate it; cheers

Ciao Max, come puoi vedere non sono proprio un principiante



Ma questo era un motore a carburatori, sui corpi farfallati si sono un principiante.

Il mio CB1100 non ha problemi, ma vorrei sapere dove precisamente collegare i tubi del vacuometro perche ci sono diversi tubi sul corpo farfallato e non vorrei sbagliare.

Mi piacerebbe controllare se le leggere vibrazioni al manubrio e agli specchi, che ho a motore caldo e in folle, sono fisiologiche o è il minimo non perfettamente alliniato.

Translated; But this was a carburetor engine, on the throttle bodies I am a beginner.

My CB1100 has no problems, but I would like to know where precisely to connect the vacuum gauge tubes as there are several tubes on the throttle body and I would not go wrong.

I would like to check if the slight vibrations in the handlebars and mirrors, which I have when the engine is hot and in neutral, are physiological or if the minimum is not perfectly aligned.




here is what i use to check carbs/throttlebodies, i have adjusted the gauges so they read equal amounts of vacuum ( see the different needle positions ).
There are several adapters, the straight ones connect to cb500 carbs, the ones above them connect to the two inner connections of the throttle body and the other 2 hoses connect to the outer t.b. vacuum connectors.

The set of three hoses are connected to the same chambers but have to stay connected because they measure vacuum for the e.c.u. ( i think, it has been a few years ago since i have checked this ) and affect the running of the engine
The little thing with the 4 connections to the right is what i use to check the accuracy of the gauges by connecting them together.

The 4 hoses should connect to the 4 brass connections which have the group of 4 hoses connected that are shown in the throttle body earlier in the thread, not the three hoses group, you should be able to find the correct connectors with the aid of the t.b. picture.

What worried me about your initial question was that you wanted to connect "the vacuum gauge" whilst there are 4 required.

If you decide to do the adjustment leave one of the screws un-adjusted so it remains in the factory position, hope this helps Enzo, all the best.