Chasing oil leak on a 1980 xs400 special

[justcallmeV]

Hi all, purchased a non running xs400 as my first motorcycle to learn maintenance and riding, finally got all the glaring issues fixed (rebuilt the carbs, soldered some connections for the headlight, rebuilt front brake caliper) and I took her for her maiden voyage the other day and... drips. It's collected around where the drain plug is (fresh photo right after I moved it so not much collected) when on the kickstand but the drain plug is dry, I believe it is coming from either the filter not sealing and the oil is dripping down or some knob thing on the crankcase (pic attached) that I have no idea what it is? If anyone knows what that is even if it's irrelevant to the leak I'd be interested. Another detail is that it only drips when parked after running, none while sitting at idle or while riding from what I can tell.

 

[BergyPatty37]

Try to chase it up higher, usually where you see the drip is not where it is coming from.
I would start with just keeping an eye on oil level consistently. If it is such a slow leak that you aren't seeing any major changes I probably would leave it for now.
If you believe one of the leaks is coming from the oil filter housing, I know the WIX 24934 filter comes with both replacement o-rings. Maybe start with that on your next oil change? Or if you replaced the oil filter recently you may have installed the filter incorrectly.

 

[Lexi]

I have the exact same symptom on my '81 XS400. It only leaks when parked and depending on how I park it, it either leaks it's way down the kickstand or trickles down to the lowest point on the engine which I believe is that piece you circled on the case. I tried replacing all of the oil-holding seals that are under the left side crank case cover (clutch push rod seal, neutral switch o-ring, front sprocket seal, shift rod seal) and it's still leaking. The only other thing I think it might be is the stator cover. If you take the stator cover off, you will see that oil tends to gather there, that's normal for this bike especially when it is leaned on the stand. There's a rubber piece on the bottom of that cover where the wires feed through, and now that I've fixed the other leaks I am still tracing oil up through that rubber piece. That's my next plan to try to fix the leak, but I haven't found the part yet!

 

[DNAPrototypeX]

I have the exact same symptom on my '81 XS400. It only leaks when parked and depending on how I park it, it either leaks it's way down the kickstand or trickles down to the lowest point on the engine which I believe is that piece you circled on the case. I tried replacing all of the oil-holding seals that are under the left side crank case cover (clutch push rod seal, neutral switch o-ring, front sprocket seal, shift rod seal) and it's still leaking. The only other thing I think it might be is the stator cover. If you take the stator cover off, you will see that oil tends to gather there, that's normal for this bike especially when it is leaned on the stand. There's a rubber piece on the bottom of that cover where the wires feed through, and now that I've fixed the other leaks I am still tracing oil up through that rubber piece. That's my next plan to try to fix the leak, but I haven't found the part yet!

I had this exact oil leak on my '81 sohc. Unfortunately the grommet was never sold separate from the stator. I found that the wires were in rough shape, so I removed the stator, cut them and removed the grommet. Then, I soldered new wire to the stator and fed then through the grommet with a little high temp silicone just in case. I only just put oil back in the bike, so I can't confirm if it worked yet. There are some pictures of what I did on my website:

https://www.pmoore.ca/posts/1981-Yamaha-XS400-Special-II-Build/#rewiring-the-stator

I hope this helps, I'll post an update if I find a puddle of oil tomorrow...