You most likely have a VH4, could be another. I just freed up a stuck valve, or maybe a sticky valve, in a V4 Wisconsin.
I had the engine off the machine. What I did was tip the engine so what ever you poured in through the spark plug hole would run into the exhaust port. I let it soak for awhile , then cranked the engine over until it had compression. Worst case is remove the intake, exhaust manifold. Then remove the valve cover and see if you can at least move it a little. If you can move it a little filling the port with oil and cranking the engine with all the spark plugs out might do the trick. Good luck