No clearance would just suggest the valve has sunk in the seat, and the rocker is holding it open a bit. Since it came on suddenly, I wouldn't expect it to be burnt, but it is possible. If you find no clearance, then adjust to spec plus some. Do the compression test. That will tell you if the valve seals or potentially burnt. If the compression reads low, I would still do the squirt of oil in the spark plug hole, and recheck, which will tell you valve or rings. If at that point, the compression still doesn't raise in that cylinder, that would make a burnt valve a likely culprit. Again, you probably know this, but don't forget to hold open the choke and throttle plate when doing he compression test, so it gets a good slug of inlet air.
Last edited by drdoug; 04/08/2019 1:42 AM.
