roger 04 rt
New member
...
Johnny, there's nothing holy about the friggin' blue paint. If you have and can use a good DVM to check & adjust the TPS (several on-line articles are available, here, on the R.A. tech pages, and in the ADVRider pages), and you know how to balance the throttle bodies, there is nothing to be lost by just doing it. Heck, it may even be as simple as backing out the BBS's another eighth- or quarter-turn each. But Roger is right too in that there's no substitute for the scientific method of seeing exactly what's happening in there.
What I think is important about the blue paint is that alpha-N fueling like the Motronic uses is very sensitive to throttle angle for the first few degrees of throttle rotation (see the +/-17% power variation for +/- 1.5 degrees throttle error in the chart below). Therefore it is important that the same air flows through each TB. Our vacuum sync is something of a proxy for the amount of air flowing but isn't a direct measure.
When the factory aligned the throttle stops they had the benefit of flow equipment, which even the Bing rebuild service said they lacked when I asked them.
When you use a procedure like zero=250, with clean throttles and clean BBS channels, we're, in effect, using the bypass channels as an airflow reference, hoping that each channel passes the same amount of air at the same number of BBS turns open. Of course the vacuum draw from each cylinder is probably different so even if the bypass hole in the TBs are equal, you still may not be able to get equal flow at small throttle angles.
For these reasons, I think the BMW recommendation to leave the throttle stops as set is smart.