Your lucky to have found it that way, my first cb550 was a project basket case (my first), took a long time, lots of trying things before it ran, stopped and started well enough to try an mot, oil pressure light 'behaved' itself but engine started going rough, I turned for home but a the lhs conrod locked itself solid on the crank, oil smelt of petrol so I'd geuss I'd left the tap on with the bike on it's stand and washed the oil off the bearing, the petrol comtaminated stuff wouldn't have then been up to the job at a geuss, it cirtainly went all frothy.