# Orientation of Throttle Plate in Stihl / Zama carburetor



## RWL (Nov 29, 2022)

The carburetor is a Zama C1Q S30c from a Stihl BG75 leaf blower. I needed to replace a broken torsion return spring on the throttle shaft and had to remove the throttle plate to get the shaft out. Unfortunately I didn't take a photo before I took it apart and didn't take note of the orientation of the hole and notch in the throttle plate. No clues on the throttle shaft. The photos are from after I had it apart and are to illustrate those two features. The throttle plate screw faces toward the engine side when the carb is mounted, so you can't get to the screw / throttle plate to change position without disassembling the carb from the blower. I put it back together with the tiny notch at the top roughly in line with a hole from one of the jets and the hole in the throttle plate completely blocked by the shaft. It runs, but it slowly dies when left to idle even with the idle screw turned to it's highest position and I'm not sure it's getting up to full speed compared to the sound of my Echo blower. I tried looking on line for this carb, but I'm getting generic Zama C1Q carb pictures and I'm not clearly seeing how the throttle plate should be oriented. Does anybody know how the hole and notch in the throttle plate should be oriented and what they're there for?


----------



## rocketnorton (Nov 29, 2022)

plate should be able to completely close
maybe the edges have a bit of angle on em
if the idle screw is not holding it open in pic, then its backward
not sure on notch


----------



## RWL (Nov 29, 2022)

Thanks. I'll have to look, but I think the plate was able to close completely. There is no flat on the opposite side of the shaft and the shaft can't be turned 180º because of the location of the arm on the one end so the plate can only be on the side facing the engine. I would think the hole in the plate would have a significant impact on idling. Where the hole and the notch should be is probably the main thing that needs to be adjusted. If it weren't for having to take everything apart repeatedly, I'd just start rotating the location of the hole and notch to see where it ran best, but I thought I'd ask people more likely to have a similar Stihl carb or who may work on these first.


----------

