It wasn’t until I gave the CB350 its first fresh fill-up at a BP a couple miles away from my house that I discovered a serious issue. When the fuel tank was full, and the bike was accelerated or leaned slightly, gas would start pouring out of the fuel door on top of the tank. Any time the bike was not standing perfectly straight, there would be a leak going down the side of the tank.
Naturally I was worried that the gas would flash-ignite when it struck the cooling fins of the motor, so I pulled over and put one of my socks over the fuel door to help keep the leak manageable. I kept my acceleration and turning to a minimum on the ride home
Luckily the fix for this was simple. I just needed a new gasket to replace the seal where the fuel door meets the tank. This was Honda part #17534-323-300. I ordered it from ebay and it came in the mail today.
The old gasket was missing a chunk, rotted, and brittle. The new one was …the opposite of those things. No more leaks.