[CamRoseCohen]

Hello,
I started my CB450 twin engine before realising there was a significant amount of fuel in the oil. The left side crank case cover gasket blew out and leaked. I didn't run the engine for very long and have since drained all the oil and will replace it as well as reseal the left cover. I am looking for advice as whether the engine might have suffered any damage from this? And what to keep an eye on. It was running for no longer than a minute.

Thanks

 

[circling the drain]

I assume you're talking about the DOHC 450 since your post is in that section, and I assume you mean left crankcase cover gasket (clear typos above). I'd also check the clutch rod seal under the front sprocket cover as they can pop out easily under crankcase pressure, which was likely generated by fuel in the oil because either the petcock leaked in the off position or you merely left it on when parked. The 450 carbs are somewhat known for this and you should always turn off the fuel when you turn off the key. Since the DOHC 450 engine often suffers cam lobe and follower damage due to slow oil flow to the top end when cold and not carefully warmed up properly, I'd advise pulling both valve covers to inspect the cam lobes to see if there is any excess wear or galling from running with badly diluted oil.