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I have a 2021 YZ125, It has started to leak oil out of the powervalve cover on the side of the motor and its dripping down the front of the motor down onto the frame. I've already replaced the gasket and the rubber seal that goes on the outside of the cover and its still leaking. Anyone have any suggestions on what I should try next? I've added a picture with the area circled that the leak is coming from. Thanks for any info
Have you had anything done to the cylinder lately? If the seal in the cyl around the shaft to the actuator arm is missing I guess it could leak there. That oil is dripping out of the vent hose on the other side is std.
I've done the top end twice now. Bike has 65 hours on it, last top end was done roughly 10 hours ago and I cleaned the powervalve at that time. The little seal around the shaft is the original one so I may replace that and see what happens. Its always leaked out of the hose on the other side which is normal but this has just started recently
I have a 2011 and a 2008 model here in my shop (mine and a friend's) that don't leak there after a billion hours.
I bet the seal in the cylinder on the power valve shaft is bad, or the seal in the large engine cover where the actuator shaft comes out is bad.
Pull the pipe and pull the linkage cover off the bike.
if the oil is dripping down from the PV shaft near the top of the cylinder casting, pop off the linkage (8mm T-handle and holder pin) and swap out that seal. While the seal is out, check the shaft for wear or damage where the seal runs on it.
I lightly grease them on assembly and they last 60 to 80 hours (four top ends) before I have to mess with them.
If that upper shaft is not leaking oil, it's the seal in the engine cover... Dump the coolant and lay the bike down on the chain side, pull the brake pedal and large engine cover (large clutch cover) You have to remove a couple of socket-head screws on the PV linkage to slide out the PV actuator shaft... The seal is easy to replace. While that cover is off, check for excessive play between that actuator shaft and the bore in the cover. You should have the seal removed to check for play. Those bores wear out and leak on the YZ250, but the YZ125 cover seems to last a LOT longer. Check the shaft for wear or damage where the seal runs.
Thanks for reminding me that I need to swap the worn out / leaky engine cover and PV linkage off of my YZ250.
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