Stuart - If the valve were burned, then you would get the fireball (when that cylinder fired), but if an intake valve were simply sticky, it could be slightly open on compression stroke (thus pressure and the spray), but still close sufficiently by the time of ignition to not have the fireball.

Purney - If the engine has set without running for a number of years, this condition is quite common, and often, will clear itself with use.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop