Do you have a vacuum comparison guage? You need some kind of guage setup to work on the TB sync.
Here is what I would do:
-perform a valve clearance check/adjustment to ensure everything is in spec. (this does make a difference!)
-Ride bike for 10-15 minutes, make sure it is fully warmed up.
-connect your vacuum guages to each throttle body.
-ensure that there is throttle cable slack on each throttle body. You don't want the cables holding the throttle plates open at this stage.
-set the brass air screws out equal turns on each side. Start with one and a half turns from bottomed.
-start engine (it may not want to idle, so open brass screws another half turn till it idles)and check vacuum guages.... see how far out things are at this stage.
-adjust throttle stop screw(s) so that each throttle body is set-up exactly the same.
-Once the throttle bodies are adjusted so that the vacuum is exactly the same at idle, start to remove slack from the throttle cables so that vacuum stays the same on each side as the throttle is opened.
-above all, you want the throttle plates to rest on the stops at idle and the cables adjusted with enough slack to allow this to happen. DO NOT tighten the cables too much as this causes the throttle plates to "bounce" at idle and wears out the throttle plate shaft bores quickly.
I think that about covers it, Post back if you have questions.
Thanks for the reply but I am afraid this is completely wrong. I have found a solution. The throttle stop screws on the R series bikes have to be reset using a voltmeter on the throttle sensor. Adjust the throttle stop screw on the left side so that a reading of .370 volts is registering on the red/white wire....then set the right throttle screw to synchronise with a manometer. Then it is possible to synchronise the cables at different throttle openings.
Yea, whatever you think. Ya know I did 3 years of BMW factory training etc (instructor and internet) and worked in a dealership under another Master BMW tech, so I kinda know my stuff.
Actually BMW calibrates each TB in the factory with a flow bench and then you set the throttle pot AFTER the mechanical stuff is done.
Best of luck to you and the internet heresay
I am sorry you feel undermined by my reply, that was not my intention at all. I am aware that BMW preset the throttle stop scew, hence my dilemma when it has been altered. The preset can only be resinstated with a voltmeter reading from the pot (.37 volts from the red/white wire on the TPS) . To suggest that it can be reset to the factory preset by some haphazzered setting is wrong....sorry.
Throttle Position Sensor - Bob Gorman
The throttle position sensor is located on the left throttle body. It is the black box
with an electrical plug extending from the bottom. The sensor is what ties the
mechanics of the throttle cable to the electronics of the Motronic.
The Motronic needs to know the position of the throttle so it can regulate gas
flow, timing, and other engine management functions. As you turn the throttle,
voltage is adjusted up and down in the sensor and relayed to the Motronic.
If you pull down the rubber cap from the electrical connector on the sensor
you will notice 4 wires. The wire closest to the rear (number 1 – red/white) is
effected by throttle openings up to 1/8th turn. Most surging occurs at very small
throttle openings so we want to make sure that the baseline voltage is correct.
Our goal is to equate a closed mechanical throttle with .370 to .400V.
Place the positive lead of the DVM (Digital Volt Meter) up into the plug
corresponding to wire number 1(red/white). On the newer bikes there is an
internal seal around the wire so use a needle or paperclip to penetrate the seal
and make contact with the wire. Attach the ground wire to a good unpainted bolt.
Turn on the bike but do not start. Note and record your initial TPS voltage so
you can go back to it if necessary. The voltage should read between 370 -
400mV. If not you'll need to loosen the two screws holding the sensor in place
and slowly rotate it one way or the other until the correct voltage is achieved.
Don't worry about messing it up, you can't. After the sensor reading is set,
tighten the sensor screws.
One last step, if the voltage during the setup process went above 400mV then
a fault may have been generated in the Motronic. This is easily reset by pulling
the number 5 fuse from the left and then replacing it. The Motronic is now reset
and the throttle position setting is right on spec.
The point you are missing in all that prose above is the FACT that you still don't have a benchmark to set things to. Neither the throttle stop screw or the adjustment of the TPS is set to a known value. Who knows how many times it was adjusted or to what value. The bottom line is that to really set the throttle bodies back to factory standards requires replacement of at least the LHS throttle body with a factory set unit. From there you could set everything up correctly. Without a know factory set throttle body you are simply guessing.
I have been involved with resetting a few bikes that were setup by owners and the procedure that I detailed in my original answer will get you close. You would still have to check the TPS voltage after the mechanical adjustment is complete.
I have just run through the procedure outlined in the 'prose'....not my prose but that of Bob Gorman. The left TS screw was adjusted so that is was clear of the adjustment plate.The TPS was set to as near zero as possible (.006V on the red/white wire which measures the tickover voltage of the throttle stop screw) The throttle stop screw was reset to get a reading on the same wire of .37 V...the rt throttle stop screw was synced with the left with a manometer with the brass air screws just seated....the engine ran quite smoothly now....then air screws were synced....and the engine ran as sweet as a nut.....so it seemed to have worked....I hope this might be helpfull to others. Thanks for your advice satguy
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