Ok, not everybody says that those sacred screws should not be touched. Reassuring news.
This being said, when reading through the subject that you mention, the certainty of starting at the good starting point is generally questionned. And apparently, when wishing to make a synchro, everybody's first gesture is to plug the Carbtune on vaccum plugs and start the engine.
I am convinced that it is too fast. For me, if a synchro is bad, the thing to do is to demolish it and make a brand new one, starting from scrap. This is why:
This is a K100 throttles assembly, direct from my barn. It is under no constraint, its sacred screws have been completely removed. The central "idle regime" screw is unscrewed as well.
For adjusting it - on the bike, no need to dismantle it - the TPS must be freed (or removed), as well as the gas and choke cables.
Clicking on the image to see better, it is noticeable that the throttles openings tend to be more and more important when moving from left to right, i.e. from the bike front to back.
That, in itself, is somehow strange because once the throttles are separated from their holding rail, the first three are very similar, all of them fitted with a return spring bringing them in closed position which, even free, is not what appears on the image.The fourth throttle has no such spring.
Here they are, separated from their rail, except the last one, shown wide opened:
The spring, when present, completely closes its throttle, by pulling
down its RH side lever. The first throttle has only one lever, on its right side. The last throttle, without spring, has also only one lever, on its left side. The central throttles have a lever each side.
On K1100, for a non obvious reason, the third throttle assembly has no spring. Maybe because of the K1100 gas handle design which would have made the necessary opening effort uncomfortable against 3 springs.
Anyway, now comes the interesting bit: the junction between throttle 1 and throttle 2
Sorry for the orientation upside down, I was looking for light
On those images they are just next to each other, both of them closed by their own sping. The junction assembly between them is extremely slack, with a gap of about 4 mm between the respective levers. That gap is supposed to be filled by the first adjustment screw, keeping in mind that:
- the opening instruction comes from the gas cable, i.e. from the right for the first two throttles.
- the RH levers can only move upwards, as in the other direction the throttle is blocked against the tubular body. Tightening a screw too much opens all the throttles located on its left.
That is the level of the first throttle RH lever when that throttle is in sure closed position (on this image it would be the same if the screw were absent):
And that is the same lever position when the screw has been screwed to its maximum:
That means that the good time to stop joining the two together is when the first throttle RH lever begins to raise. If it raises you went too far.
Once that optimal relative position has been found, the counternut can be tightened.
Same operation for the screw between throttles 2 and 3. Make sure that the central wrongly called "idle speed adjustment screw" is far from its contact plate. When ajusting the second "sacred screw" check that the RH lever of the FIRST throttle does not move up. If it does you have gone too far. The purpose of the game is making sure that all the throttles are well closed together, the reference one being the first one. Here again, once the correct adjustment screw position has been found, the counternut can be tightened.
Once the junction between throttles 2 and 3 has been achieved, it is time to put the central "idle spleed" screw just against its plate. The purpose of that screw is to prevent the throttles to act as stop pieces when the ramp arrives in closed position. Steel against steel is more resistant than brass against aluminium!
Finish with the adjustment of the junction between throttles 3 and 4, still making sure that the RH lever of the FIRST throttle does not move up. Once more, tighten the counternut when it is finished.
That is it. You have spent 10 minutes and are then on a sure correct basis. It is then time to reconnect the gas and choke cables and to play with the Carbtune for the final
fine tuning. If it goes beyond control, redo from start.
At the very end, adjust the TPS. And then, when you tell the Jetronic or Motronic that the throttles are in closed position, they are, which implies calculations on solid basis.