How do you set throttle body butterflies?

[RSSSSSSS]

Ok, I've messed with my throttle body butterflies (you know those marked screws on the bottom of the bodies that you aren't supposed to touch) on my 94 R1100rs. Now I'm trying to get them back to stock or close. I'm experiencing some hard starting issues that only happen when the bikes cold. Once it's started and warmed up it always restarts easily. Allow it to cool down and the hard starting resumes. The plugs are new, new plug cables, good coil (tested) good hall sensor, valve adjustment good. Throttle sync. done. The timing seems to be fine, Fuel filter changed, plenty of fuel pressure at injectors, compression is 145psi on both sides. zero=zero done on TPS. Bike has 33,000 miles on it. Also fitted with an older techclusion so the O2 sensor is disconnected.
The only info I can find online is that the butterfly angle at closed should be 10 degrees. Problem is I don't know how to measure that to adjust them. I set them as follows: Loosened all cables, adjusted both throttle bodies so that the bike would idle at 1000 rpm (with tps @ lowest setting and BBS all the way in, techclusion disconnected). At this point the 1000 rpm was synched using a manometer for just the throttle bodies. Then I used the BBS to raise the idle to around 1100 (still synched) The next step I set all the cables at idle and at just off idle (again synched). Still hard starting when cold. I have to use fast idle switch and crank open the throttle for ten or so operations of the starter to get it to finally catch. Any ideas on what else to try? Sorry for the length of this but wanted to give all the background I could think of.
Larry

 

[jammess]

Hey, I messed with my butterflies also and with, I think, good results. The way I did it was I removed the large brass screws, cleaned them, re-installed them and gently seated them then backed each out 1 turn. I then started up and adjusted the butterflies at idle for sync as indicated on my twin max. I left the brass screws at 1 turn out. I think this is the proper way to sync these TBs because the brass screws are like mixture adjustments on carburetors and one does not sync carbs by adjusting the mixture screws one adjusts butterflies at idle to achieve sync. Same as adjusting Bing carbs on airheads. Then roll up about 3K on tac and adjust cables for sync. I know the TBs are a matched pair with butterflies set on a flow bench yadda..yadda... but what can I say this method seems to work for me and the twin max isn't lying when it shows equal vacuum on both TBs.

 

[RSSSSSSS]

Thanks Big Red. I'm thinking the same thing...if the butterflies are synched and the BBS's dialed in, and the cables synched it ought to be balanced correctly. However mine is still very hard starting when cold. I'm hoping someone can point me in the right direction

 

[gsaddict]

If you PM Poolside at Adv Riders and beg nicely he has a written proceedure to correctly reset them.

 

[PGlaves]

Thanks Big Red. I'm thinking the same thing...if the butterflies are synched and the BBS's dialed in, and the cables synched it ought to be balanced correctly. However mine is still very hard starting when cold. I'm hoping someone can point me in the right direction

OK - one difference is that on carbs the idle mixture screws usually meter fuel. On the R11xx throttle bodies they are air bleed bypass screws. So they effect vacuum, so they effect balance.

The hard starting cold means that the throttle plates and or air screws are admitting too much air for the small amount of fuel injected. I would close the bypass screws and open them 1/4 turn, then balance the throttle plate adjustment at as low an idle speed as I could reasonably - say 900 rpm. Then open the bleed screws to an 1100 rpm idle, in balance.

 

[RSSSSSSS]

Thanks Paul, I'll try that tomorrow and see if it improves starting. I admit I was thinking just the oppsite (old school airhead thinking).
Larry

 

[RSSSSSSS]

Well, she is starting fine again. Thanks to Paul and others advice. I also read more about throttle bodies and TPS then I would ever want to know over at ADVriders. Interesting reading though. I haven't had a chance to take her out for a test ride but here is what I did. Turned off the Techlusion. Loosened cables so no interference with butterflies, Backed off throttle positioning adjuster on both sides until they would just make contact with the butterfly. Set TPS to .005 (lowest setting on mine). Started up bike to get it to idle. (had to fiddle with the butterfly adjustment here to get it to sustain idle around 900) . I then used my manometer to balance the throttle bodies using the positioning screws. Using the manometer I adjusted the BBS's to further increase the idle to 1100. Set the TPS with a digital volt meter for .385 v. Adjusted the left throttle cable to about .5mm of slack. Synched the right throttle body to the left using the right side cable adjuster for just off idle (2000rpm). Reconnected the techlusion. Pulled the #5 fuse for 5 minutes to erase any error codes. Reinserted, turned on the key, manipulated the throttle from full stop to wide open a few times. Turned off the key. Now the bike starts up reasonably well.

 

[JimMoore]

You may want to consider putting a drop of blue loctite on those throttle screws. I lost a screw after I played with them, and they're a litle difficult to replace. They have super-fine threads.

 

[RSSSSSSS]

Good idea Jim. Thanks! I'll do that.

 

[jammess]

Uh, that is a good idea. Got some blue loctite which should be Ok. Better that than the screw backing out for sure. Got to remove tupper ware but what the hey.