This is my first time on this forum I am on a couple of others, I have been riding since I was 16 I am now 80 and still riding. I have had a variety of bikes my earliest were British Matchless and AJS there have been several in between but now I have a 96 Rebel 250 and it has 57,000 kilometres on it. The bike developed a severe rattle under load sounded like broken piston or rings, and sometimes like detonation but severe. I disassembled the engine to find nothing broken or badly warn, however there was excessive oil/carbon on one cylinder which leads me to believe the noise was detonation. I an doing the usual, rings, honing, valves and seats and gaskets. Something I had noticed inside the alternator housing, there was evidence of water possibly as much as a cup full. There was a rust mark on the spacer plate about an inch high. I noticed a drain hole in the bottom of the housing that was plugged with dirt and not allowing the water to drain and therefore rusted some of the parts. With the drain plugged, conceivably the housing could fill up with water and cause problems with the alternator. The drain is there for a reason and water can get in past the starter, however it is of no consequence if it can drain out. I was reading a post about no spark and the PO mentioned that he had a fully charged battery, the battery does not provide the spark it comes directly from the alternator and the battery only provides power for the lighting and horn. I found this out by accident when my battery fried and I bump started it and it ran just fine with a dead battery. Photo of plugged drain.