I posted back in 2010 about questions on how to adjust this screw on the back of the pump. I now have a new update on how to do this and have yet to find it on this site. My pump is a R20Y US. It has both the starting and fuel cut off solenoid.
The issue was that when I removed the cap screw leading to the rack adjustment screw and inserted a slotted screw driver into the hole, I hit a spring loaded lever. I could never engage the screw. The suggestion was to remove the starting solenoid above and that would make it easier to see the rack screw. Well it did increase visibility, but I still could not insert a screwdriver through the hole and engage the rack screw because of this lever. The lever turns out to be the one that the starting solenoid contacts to richen the pump.
I contacted a friend of mine in Germany who professionally rebuilds these pumps and asked for help. I have a two plunger pump on my 220SE and know there is a screw on the side of the pump that will move the lever out of the way. Turns out this pump has the same screw although is on the opposite side, the side facing outward. It is a cap screw with a 14mm hex. Loosen it out almost where it touches the lever on the pump. Behold! The rack screw is now exposed!
Now inserting the slotted screwdriver you can feel the screw and easy to click in either direction. Just tighten the 14 mm hex back up and you are in business. With this tip, removing the starting solenoid is not necessary and didn't really help all that much.
Yes, you can do the same by changing shims on the BC. My problem was I needed to lean the pump and only had the factory 2mm hardened shim. No way to go smaller unless I made new ones. That factory shim is hardened and a special size to fit in a recess. I didn't want to go there. I just now need to adjust the idle speed knob and i'll be back in business.
