Had to replace the water pump in my 1999 Honda Accord EX, and when I opened the timing cover I noticed this mangled rats nest jammed against the water pump! At the time I had no idea what this belt was, but given how mangled it was I knew it had been like that before I even purchased the car a few years ago, and therefor not critical! I debated omitting the belt, especially since I know it's not required (Obviously), and I DON'T know why it broke in the 1st place (Possibly age, possibly shaft seizure/damage), and as any competent technician knows, repair is not just identifying the problem, but finding out why there was a problem in the 1st place! If it broke due to seizure/shaft damage, given the fact that the Timing shaft is coupled with this mystery shaft, if it does sieze again, with the belt being new and strong, it WILL DESTROY THE ENGINE! But given the age and mileage (33X,XXX on the odometer) of this car, Age/wear certainly can't be ruled out! Plus both shafts the belt controls turn very smoothly, so I decided to replace the belt with everything else! A quick Google search shed light on this subsystem as a Balance Shaft used to mitigate engine vibrations with counterweights! Quick trip to an auto parts store and I have the new belt in hand, but how to time it to the rest of the motor? I could not find a guide anywhere online on how to time the Balance Shaft if it loses timing with the Crankshaft, and I don't have a Haynes Manual, so I had to depend on my technical muscle and analyze a few of ‪@ktecgarage‬ videos on rebuilding an F23 Honda motor to determine the right way to align the shaft! I learned that the shaft closest to the front of the car is 1:1, line up the notches and ur good 2 go, the shaft closest to the water pump is a different story. The gear that the belt drives is coupled internally to another gear that makes 1 full revolution for every 3 revolutions the outside gear makes! To put it in plain English, The alignment markers mean NOTHING unless that external gear is on the correct revolution! As shown in the video, the gear will not rest on those markers unless its on the correct revolution, so if you line up the shaft and it moves, spin it 360 and try again, untill the shaft rests on the markers shown in the video. There is also a 12mm bolt behind the motor right next to a VIN Plate used for aligning the shaft properly, but you will lose a little oil, so if you go that route be warned. Just wanted to put this video out to shed some light on this Balance Shaft and how to properly align it if the belt breaks and/or it loses timing somehow, bc from my experience, documentation is slim on how to time this shaft after it loses timing from the Crankshaft! Thanks for watching!!!
Note: I am NOT a career mechanic! I am just a competent General Purpose Technician that believes DIY knows no limits!