TOPIC:

So I spun a rod bearing on my KZ440. It was the left-side cylinder (Is that #1 on this bike?), and the bearing, rod, and that crank journal are all pretty thoroughly ruined. There's actually melted bearing material plugging the oil galley ports on that journal.



It's pretty clear that rod bearing got way too hot. Both halves of the bearing are fused together, and the rod cap has discolouration due to the heat.




While we were taking the engine apart, we found a lot of varied organic detritus within the crankcase. Mostly maple seeds, a few twigs, and some leaves. I'm thinking that a previous owner decided to change the oil under a tree, and most of this junk got in there through the open filler hole. There wasn't anything plugging the oil screen in the bottom of the crankcase (next to the oil filter), but there was definitely some in the bottom of the crankcase. I haven't yet taken the oil baffle out of the bottom of the crankcase to check if there's junk in there yet, but I'm not expecting it to be clean.

The main bearings, the other rod bearing, and the rest of the journals are all in pretty good shape. The pistons as well are looking really good too, apart from some carbon buildup on the tops. Both rotate completely freely on the wrist pins. Additionally, the cylinder bores look to be free from any scoring, and still have some of the factory crosshatching towards the bottoms of the bores. The top end looks pretty good as well and the valves appear to seat well.

I know that at a minimum this engine will require a new crankshaft, new bearings, and at least one rod. And from my research (this would be my first engine rebuild) I should probably replace both rods, to be on the safe side. But, assuming the oil galleys and ports are all cleaned out thoroughly, is there any reason one couldn't just replace those parts and put the motor back together?