1995 RT1100 TB's won't synch well on low idle

[costellon]

Hi all, a mate recently got a 95' R1100RT in a sorry state. Much work later it's as clean as a whistle and I just can't seem to synch the throttle bodies correctly on low idle.
OK, compression is a little low on both cylinders (120psi on both) - but when I set both brass screws to 1.5 turns out and connect up the manometers the left TB (TPS side, with TPS correctly zero'd) registers on the manometer but the only way that I can seem to synch the right (or in fact get any reading on the manometer at all) is by screwing the brass screw in so that it's only a 1/4 turn out. The manifolds are good and sealed tightly, "o" rings on the brass screws are new .... any ideas ? I have done this before many times and normally the screws just need to be fractionally turned to synch them up. Any advice would be greatly appreciated, thanks.

 

[GORILA]

Probably the throttle butterflies are worn. You can have them refurbished and there is a bloke in Romania who sells self repair kits (Dan Cata on AdvRider). Alternatively you can check the butterfly gap with feeler gauges, to see if they are equal on both throttle bodies. I believe these were often set up wrong at the factory. The throttle body that doesn't respond to changes in the idle screw probably has a much too wide gap. Adjust the gap to be the vsame as the throttle body which responds correctly to the idle screw!
regards.

 

[costellon]

Thought as much, thanks M8.

 

[DrFarkoff]

I just can't seem to synch the throttle bodies correctly on low idle.

You wont! the bike needs to be at operating temp (5 bars on RID) and Idle should be 1100 ish plus or minus 50 rpm

If you are trying to set it lower than that you are wasting your time

Also do not run it on centre stand trying to warm it up you'll burn the paint off the wind deflectors down by the exhaust headers OR maybe even set it on fire

 

[costellon]

You wont! the bike needs to be at operating temp (5 bars on RID) and Idle should be 1100 ish plus or minus 50 rpm

If you are trying to set it lower than that you are wasting your time

Also do not run it on centre stand trying to warm it up you'll burn the paint off the wind deflectors down by the exhaust headers OR maybe even set it on fire

Thanks for your advice. After owning 2 GS's and four RT's I am aware of the protocol involved in a throttle body synch. As a precaution I normally remove the shark fins when doing this job and stick a large fan in front of the machine in order to prevent overheating. I have never seen a BMW throttle body not register anything on my manometer at tickover with 1.5 turns of the BBS. I suspected worn butterflies and wanted a second opinion.

 

[bimmerboxer]

After ensuring there are no leaks in the system, a mate adjusted the throttle flap stops on my 2001 GS. Most manuals discourage this.
He said, sometimes the flaps go beyond vertical and actually stop when it sticks to the walls of the throttle body and not against the 'stop'.
So he walked around, a throttle body in his hand at a time, pushing the flaps open with his fingers and adjusting it till he was satisfied that the stops were just right, ie the flaps resting against the stops at the lowest possible point. Best done over a beer or two.
He then did a sync.

I was amazed at the results. It was like off the showroom floor, even better. The performance too, was unbelievable. Maybe he slipped a NOS system in there, I do not know.

See for yerself.
http://www.youtube.com/watch?v=tiXzAJWWkUI

http://www.youtube.com/watch?v=uu9yXMtrTYw


Hope this helps!

 

[costellon]

Thank you chaps !