07-16-2024, 10:04 AM
Update. I think I may have solved it, or at least massively slowed it down. Last weekend I drained the oil to get a look at the sealing surface on the sump and take another look at the plug. I ran my finger over the area on the sump and I can't feel anything there. Here's a bad photo of what was there:
I did grab a little Brillo pad, some solvent, and gave it a good going over to be sure there wasn't some rogue gunk on there. Seemed like a dead end though. So, I turned my attention to the drain plug. Still, it looked fine and I couldn't feel anything strange on the flange surface. But that didn't necessarily mean that all was good. I had a look at the sealing surface under a microscope and along the edges of the flange you could see areas where the plug had been beat up, raising a few very small burrs along the outside edge of the sealing surface. I don't remember ever dropping the plug, but that doesn't mean I didn't. I just don't remember. The burrs were very small, raised up probably .005" or less and couldn't be seen with the naked eye. They were on the perimeter and that raised a question of if they even mattered. I put on the old crush washer and sure enough, the outer edge rested on the burrs. Smoking gun? I don't know. You would think that the crush washer would deform enough to seal the small discrepancy in the surface.
I grabbed some stones from the bench and went to work on the flange surface. These are not ordinary garage stones, they are very fine, very square, very flat, stones used for gunsmithing work. It didn't take long to burnish the burrs off. On with a new crush washer, torque to 31 ft-lbs (42 N-M for you metric types), fill with oil, and see what happens. So far, no hideous oil slicks under the bike. I'm not totally convinced that I've solved the issue. Time will tell that. I do know that on the next oil change it will be getting a new, carefully examined, drain plug.
All of this still boggles me. There is nothing I found that the crush washer shouldn't seal around. We're not sending people to the moon here. Just trying to keep fluid from leaking out of a hole. This is definitely not brain surgery. But, then again, I'm an American engineer, not a German one. My idea of precision for a specific application may differ.
I did grab a little Brillo pad, some solvent, and gave it a good going over to be sure there wasn't some rogue gunk on there. Seemed like a dead end though. So, I turned my attention to the drain plug. Still, it looked fine and I couldn't feel anything strange on the flange surface. But that didn't necessarily mean that all was good. I had a look at the sealing surface under a microscope and along the edges of the flange you could see areas where the plug had been beat up, raising a few very small burrs along the outside edge of the sealing surface. I don't remember ever dropping the plug, but that doesn't mean I didn't. I just don't remember. The burrs were very small, raised up probably .005" or less and couldn't be seen with the naked eye. They were on the perimeter and that raised a question of if they even mattered. I put on the old crush washer and sure enough, the outer edge rested on the burrs. Smoking gun? I don't know. You would think that the crush washer would deform enough to seal the small discrepancy in the surface.
I grabbed some stones from the bench and went to work on the flange surface. These are not ordinary garage stones, they are very fine, very square, very flat, stones used for gunsmithing work. It didn't take long to burnish the burrs off. On with a new crush washer, torque to 31 ft-lbs (42 N-M for you metric types), fill with oil, and see what happens. So far, no hideous oil slicks under the bike. I'm not totally convinced that I've solved the issue. Time will tell that. I do know that on the next oil change it will be getting a new, carefully examined, drain plug.
All of this still boggles me. There is nothing I found that the crush washer shouldn't seal around. We're not sending people to the moon here. Just trying to keep fluid from leaking out of a hole. This is definitely not brain surgery. But, then again, I'm an American engineer, not a German one. My idea of precision for a specific application may differ.