Inspect the engine case cover very carefully around where the front sprocket is. If you see any grooves or markings around that area it's probably a result of a loose chain hitting or rubbing against the case cover. I had the same problem and thought it was the o-rings which didn't resolve the issue. I eventually cleaned up the entire area and discovered that the oil was coming from further up and making its way down into the slave and making it seem like the oil was coming from the pushrod bore. I removed the case cover, cleaned up both surfaces, and resealed with gasket sealer and all is well.