F800GS throttle body balancing?

[Jonnie Boy]

Anyone know about throttle body balancing on the 800GS?

No mention in the Haynes manual/service schedule and not seen on any BMW schedules either. Unless Im being dim and missed them!

Assuming that there must be some sort of matching/balancing required!? or is there some mystical techno involved so this done automatically?

I stand by, waiting to look stoopid by a really simple explanation!

 

[v8legend]

I've wondered about this. A mate has just had his F800GS serviced at NOG, and can't believe how smooth it is now. They must have done something?

 

[Micky]

Never had to have mine done, 51,500 miles now and still as smooooth as a babies bum

 

[Jonnie Boy]

Factory set perhaps? No further adjustment required? even after twiddling the valve clearances? Always had to adjust on every other twin Ive had, albeit V's and Boxers..........

Mmmm time to get the spanners out and have a play!

 

[Jonnie Boy]

The throttle bodies are synchronized at the factory using a specific flow bench. It is impossible to get this degree of accuracy using normal tools. The throttle bodies are rigidly attached to each other with a direct linkage. The adjustments are paint sealed at the factory. Do not adjust the linkage! It will never be correctly set for balance and closed throttle flow again. BMW tells it's dealers to replace the tampered throttle body set with a whole new part (no warranty). The technicians are taught not to make any adjustment to the sealed system. The fuel injection system can not compensate for the throttle body idle stop and matched flow. The engine will be out of calibration at all speeds. It is an expensive mistake. There is no reason to adjust as it stays true for it's service life if not tampered with. Other BMW models with this no sync requirement include the all years K bikes, R1200C.

If you suspect uneven initial throttle lag you may want to check the valve clearances to insure they are within spec and as evenly balanced as possible.

The idle air is controlled by the idle valve to both throttle body bypass ports. It is assuming a specific closed throttle flow through the throttle bodies and adjusts to add to that flow to reach a target idle speed depending on coolant temperature and system voltage readings. There is only one air bypass valve to both throttles so exactly equal flow from both throttle plates must be present for the idle to work properly. This same idle bypass valve remains somewhat open and blends with the throttle opening at speed. The idle valve is adaptive and if the initial closed flow is off of calibration it will adapt to compensate thereby affecting the open throttle ranges. This will result in too lean or too rich mixtures which may affect performance delivery.

The fuel injection system calculates air flow by throttle opening (throttle potentiometer) and RPM. There is no mass air flow sensor (alpha-N). If the idle bypass has adapted due to incorrect closed throttle position these calculations are off. BTW the O2 sensor will read this and attempt to correct the mixture but it's range of total correction is only 5%. If you are off by more the injection can't fully compensate and if you are off less it may compensate only when the engine is fully warmed up. During warm up when the O2 sensor has not "lit up" it will not correct and the engine may exhibit cold running problems.

Bottom line of all of this is don't mess with the throttle body adjustments. You will not gain anything and likely end up with an expensive mess.

Blatantly ripped from Gr8ridn's posts on F800Riders.org

That explains that then! One less thing to fiddle with

Im gonna have to get an airhead or something to satisfy my tinkering needs!!

Did I jus type that??