NickE
Member
Recently re-built from the ground up my CB350K4, every part that could come apart from another part was removed from that part. At the time my engine guy mentioned that he'd seen CB350K4 motors with half the mileage (mine was at 22k) and twice the wear, particularly the oil pump and bottom end was as tight as he's seen. I replaced every gasket, oil seal, and even found a NOS Rubber Ball for the bottom end. Every O-ring was replaced with either oem or brand new proper sized modern o-ring. The cam was re-worked by MegaCycle and the bike pulls hard over 7k. It's a joy to ride now and I've had a blast breaking it in and riding it for the last 1500mi.
I have one issue. I have 64mm stock bores, new rings and no overbore. Good compression. The headgasket used in the rebuild was an "OEM" it had silicone "fire rings" around the oil galleries in the back of the head.
Everything was completely dry up top for 600mi after the re-build, I had just started shifting up around redline, 9k. I had to get somewhere quick one night and jumped on the freeway and held 70mph (17/36) or 6800rpm ish for 20min or so. The next morning before work I noticed that the gap at the head gasket looked damp, and after a few more trips at 70mph and up that the head gasket is seeping, likely at the galleries. I'm considering a bypass and bearing system for the cam, but honestly that's a ton of investment for a daily CB350.
I talked to a tech rep at Cometic, they can't get 64mm fire rings.. I am thinking of just biting the bullet on a nice new valve/guide/spring system, but I don't expect to spin 12k anytime soon. Overboring the cylinders and putting in new pistons and rings to match just so I can get a top quality headgasket is absurd.
What is the best way to eliminate my issue, I was thinking that a better headgasket would help, but if the best in the business at custom headgaskets can't help me what are my other options?
I want to be able to ride my bike for long distances at decent rpm, for long trips (>1hr) spinning 6k shouldn't be an issue, and 7k for 45min shouldn't burn anything up. Obviously pushing the motor at 8500 for any length of time isn't healthy, but I'd like to commute in Detroit without seeping oil.
Nick
I have one issue. I have 64mm stock bores, new rings and no overbore. Good compression. The headgasket used in the rebuild was an "OEM" it had silicone "fire rings" around the oil galleries in the back of the head.
Everything was completely dry up top for 600mi after the re-build, I had just started shifting up around redline, 9k. I had to get somewhere quick one night and jumped on the freeway and held 70mph (17/36) or 6800rpm ish for 20min or so. The next morning before work I noticed that the gap at the head gasket looked damp, and after a few more trips at 70mph and up that the head gasket is seeping, likely at the galleries. I'm considering a bypass and bearing system for the cam, but honestly that's a ton of investment for a daily CB350.
I talked to a tech rep at Cometic, they can't get 64mm fire rings.. I am thinking of just biting the bullet on a nice new valve/guide/spring system, but I don't expect to spin 12k anytime soon. Overboring the cylinders and putting in new pistons and rings to match just so I can get a top quality headgasket is absurd.
What is the best way to eliminate my issue, I was thinking that a better headgasket would help, but if the best in the business at custom headgaskets can't help me what are my other options?
I want to be able to ride my bike for long distances at decent rpm, for long trips (>1hr) spinning 6k shouldn't be an issue, and 7k for 45min shouldn't burn anything up. Obviously pushing the motor at 8500 for any length of time isn't healthy, but I'd like to commute in Detroit without seeping oil.
Nick