Often as we find old gas engines to restore, the oilers are either broken, squashed, or nonexistent. Looking for the proper sized oiler with a check ball and internal vent tube has frustrated me for years. When I did find one of the proper size, it was always a great deal more expensive than those without the check ball which are more available. As you know with the old engines, some compression gas slips past the rings of the piston and escapes out the piston/wrist pin drip oiler tube. Using an oiler with the proper check ball prevents this gas escape and the blowing out of oil intended to lubricate the piston and wrist pin. I know you, too, have seen dysfunctional oilers at the shows blowing and hissing smoke through the oiler, some like a second exhaust port. I've decided to take some of the less expensive and more available oilers and by adding a vent and check ball, make them useable for my hit and miss engines.
The first step is to disassemble the oiler and clean it thoroughly using a paint thinner. Then, steel wool all the brass surfaces until they are bright. Locate the hole in the drain tube, and 180 degrees from this hole, place a mark on the bottom of the oiler with a pencil. With the bottom of the oiler upright, clamp it into a vice and center punch on the pencil mark side one half the distance between the drip tube and the threaded area on the oiler. Now, with a 1/16 inch inch drill bit, angle the drill parallel to one side of the small drip tube so that the drill bit will exit into the oil chamber on the other side. Next, enlarge the hole from 1/16 inch to 1/8 inch and insert a 1/8 inch brass tube which will become the new sight glass vent. At this point, you should be aware that brass is very soft and that drilling brass with standard high speed drill bits will cut too rapidly. The two leading edges of each drill bit used on brass should be rubbed or dulled first with a small sharpening stone to prevent loss of control of this operation. With the 1/8 inch tube just slightly entering the sight drip area, solder it in place with a prestolite or propane torch. This 1/8 inch tube is available at most hobby stores in various sizes and lengths. I use 1/8 inch tube for number two oilers and smaller, 5/32 inch tube for oilers larger than size 2. With the vent tube in place, it can be bent toward the center and sawed off even with the bottom thread on the upper portion of the oiler.
With one-half of the job completed, let's go on to the final phase of the retrofit and install a check ball into the base of the sight glass drip section. The openings vary through the bottom of the drip sections, anywhere from 1/8 inch to 1/2 inch and larger in size. I have found steel balls available through our engine dealers work very well for this. With a drill press, invert the drip section, enlarging the hole with a lathe center drill larger than the ball to be used, and deep enough to allow a ball to be recessed. A horizontal hole 1/16 inch in size is next drilled to hold the ball in place. For this, I have used 1/16 inch brass rod also available from local hobby stores. Cut the brass rod slightly shorter than needed, crimp one end and tap it into place beneath the ball in the drilled hole. Be sure the check ball has vertical movement of 1/8 to 1/32 inch in the hole.
We now have an oiler complete with vent tube and check ball which is much like the original and useable on all hit and miss engines!