Hi guys, wonderful forum, kudos. I posted around 8 months ago about an old Honda BF100 I had acquired from a friend. After changing the oil, replacing the water pump impeller, replacing the prop, rebuilding the carb, and adjusting the valves, I put it in the test tank and was happy to see that it ran beautifully. The problem was that the oil had become milky inside of five minutes. Obviously cooling water was getting into the crankcase somehow. I inquired on this board and was informed that a cracked cylinder block may have been the culprit. I had already checked the head gasket and it was fine. Believe it or not, I just got around to checking this thing out. I can't see any obvious cracks in the cylinders or water jackets, but are the water jackets supposed to run all the way down the cylinders? The water jackets on my motor only go about 1/5 of the way down. There does seem to be a small horizontal line (which could be a crack I guess) half way down in one of the cylinders, about 2 inches long. But if the water jackets don't go all the way down, water can't possibly be getting in there. Here's the interesting part. In the Honda service manual, it shows an o-ring where the engine case sits on the lower unit. This o-ring seems to prevent water leakage from the water tube where it connects to the engine case. This o-ring was not present on my BF100, although I can see where it is supposed to go. Could the lack of this o-ring be the cause of water entering the crankcase? There is a gasket that should seal the crankcase from water even with the absence of this o-ring, but maybe the pressure is so high that water can seep in. Does this make sense guys? Any input would be greatly appreciated. Once again, great forum!
