Please bare with me, I had a thread on here before but I suppose it was so old it got deleted. So I'll post what I've got and whats happening again, in sincere hopes someone will know how to help me. I've got a 1975 KZ400S (twin) that's blowing smoke out of the right cylinder. It was suggested to remove the valves and inspect valve guides for dryness and cracking. In the process, I bent a valve. So, I got a parts bike off ebay for real cheap and threw the parts bikes head on to see what would happen, which leads me to where I am now. Compression is low but useable in both cylinders ~115psi...but god only knows if my gauge is calibrated decently. Anyway, I got a leakdown tester for more accuracy. When I plug it in the left cylinder I hear air coming thru the oil fill (past the rings) but only reads a 6% loss, and a little past the rings is fine I'm told. WHen I plug it in the right cylinder, same amount of air past rings, but 68% loss because the exhaust valve isn't sealing properly. I've had the head and cylinders off a few times. Have replaced o-rings in the head and the thick little ones at the cylinder base gasket, and the cylinder base gasket. Haven't replaced head gasket because I can never see oil on it and it looks beautiful. Cylinders aren't gouged up. Anyone have a suggestion? Been three years of restoration, and man I want to get her on the road this summer. Thanks.