Certain honda gx series engines have them and some don't. I have removed the shaft and ran them without....made no difference as far as operation. Engine revved up slightly faster due to less parasitic drag. If you remove the balancer shaft make sure you remove the bearing from the case. It's in there pretty good is easy to get out if you pack the center bore of the bearing with wet newspaper. Takes like a half hour of packing but it will come out. Do not leave it in and run the engine because it will magically come out and destroy the bottom end. Ask me how I know.