How do you un-stick a sticky valve?
Nasty problems that can bedevil you if you are running 100LLL and don’t keep the combustion process hot enough. Identify which cylinder has the sticking valve. This will be the one with a cool exhaust stack and cool head. To determine this, use your hand, but with caution, as things in there are VERY hot. Once the coolest cylinder has been determined, remove the top spark plug and rocker assembly. Then get that cylinder to top dead center, (more or less). Feed into the spark plug hole a long length of soft rope or string packing that will fill the combustion chamber. Push down on the valve and refill the cylinder until you can get the valve to bump against the fill material and push the spring down far enough to remove the keepers. Lube the stem of the valve with WD40, fit a drill to the end of the stem, and at low speed rotate the valve while moving the valve slowly in and out and spraying more WD 40. There are several lubricants available, one that seems to do a particularly good job is a gun cleaning oil, available from your local gun shop (Hopes #9). Seems this oil has an ingredient that works on loosening the lead a little better. Once you can get full travel on the valve, reassemble the rocker assembly, re-set the clearance, (You must remember to remove the packing material), seal and valve cover and you are done. Total time about 20 minutes IF you have all the tools available.