R100GS Bing Needle & Jet Replacement
Sooner or later you're going to run into someone who will insist that the needles and needle jets in your Bing constant velocity carburetors are shot, at mileages somewhere north of 30,000. The story is that the needle rubs on the needle jet and they wear each other out. I'd been noticing a drop off in mileage (to around 34 mpg on the highway) and decided, at almost 50,000 miles, to take that advice. The work took me about an hour and didn't take any special tools. I started by turning off the fuel and dropping the float bowls. I'd upgraded to alcohol proof floats a year or so ago, along with alcohol proof lines. That meant there weren't any problems getting the bowl loose, and there wasn't much sediment in the bowl itself.
As you can see, there's a big difference in the way the new floats work. So much difference, in fact, that the kit includes a new float bowl, new float needle and keeper in addition to the floats themselves (pictured at left).
The bottom of the carb (top of page) is modified as well, with a new set of lever arms to engage the pins on the side of the floats.
To get to the needle jets I unscrewed the main jet, setting it and the associated washer aside. The needle jet holder comes out next.