Seems to be a long-time problem with Harley’s that oil in the tank will drain through the oil pump and fill the crankcase. When the tank is checked it appears low and more oil is mistakenly added. Or the bike is started and the oil in the crankcase is blown out the vent all over the ground on older models, or into the air cleaner and then onto the bike and ground if it’s a newer model.
One culprit is a check valve that is supposed to prevent the drain-back into the sump. If a piece of trash gets lodged between the seat and ball, or the ball gets a groove worn in it over time, or the seat gets a slight nick in it, oil will leak past and the mess described in the paragraph above happens. A couple other problems may cause wet-sumping, too. These are a loose idler gear shaft in the pump body, or a leaking oil seal at the pump drive shaft. These last two are beyond the scope of this article.
Generally the check valve is easily inspected and repaired. It is possible that the oil pump will have to be removed for repair, and even that the oil pump body might have to be replaced. These last two are seldom necessary though. The following procedures will usually fix the problem, and further disassembly won’t be required.
First acquire five (5) new check balls for your particular oil pump model. You might not need all of them, but the unneeded ones can have an alternate use. Drain the oil from your tank, and remove the plug and spring above the check ball. You can find the location of the plug by referring to your service or parts manual. (You do have a service manual, don’t you?) Fish the ball out of the hole with a magnet. Do not pry it out with a small screwdriver or any other device. Prying it out might cause more damage by scratching or gouging the seat. Take that ball and stick it in your pocket. Don’t use it in your oil pump again.
Clean out any debris and oil. Use a flashlight and a magnifying glass to inspect the seat. If the seat has any scratches or dings in the seat, it’s time for STEP TWO. If the seat looks good, drop in one of the new check balls. With a brass drift and small (emphasis on “small”) hammer give the ball a smart rap to seat it. If you ham-hand this you will screw up the oil pump body and get the privilege of buying a new one. Now remove this ball and stick it in your pocket, too. Drop another new ball into the hole, replace the spring and plug, add oil to the tank (don’t overfill), and try the beastie out. If the wet sumping stops, you’ve solved the problem. If not, it’s time for STEP TWO.
This step is only necessary if the seat is messed up, or the wet sumping didn’t stop after performing STEP ONE. You’ll get to make a special tool to do this. That puts you in a league above 99% of HD tinkerers.
The tool is simply a welding rod attached to a new check ball. The old way of attaching it was to weld the rod to the ball by touching the rod to the ball while the rod was in a stinger, with the machine at about 65 amps. If you’re a welder, or know one, this works fine. Be careful and don’t mess up the ball, though. Another way is to mix up some epoxy glue and glue the rod to the ball. If you let it cure sufficiently, this works almost as well as the welding method. It has the added advantage of not screwing up the ball for us less-than-stellar welders. Once you’ve made the basic tool, slip a piece of rubber hose over the rod. That’ll make it easier to operate the tool.
Now to the meat: Coat the end of the ball with a very fine lapping compound. Some mechs use valve lapping compound, while others use something like Simi-Chrome. You can even use one followed by the other, if the seat damage is more severe. Put the coated tool into the oil pump and lap the seat as you would lap a valve seat, by spinning the tool rapidly back and forth in the palms of your hands, while exerting a slight downward pressure. Check progress frequently, and stop the process as soon as you have an unbroken lapped band around the seat.
Clean the seat area thoroughly. Do not flush it to clean it as that will allow the goop to get into the pump body and do bad things. Use a clean lint-free rag dipped in a solvent such as gasoline (horrors!) or even lighter fluid (more horrors!). Gently wipe the seat area until all traces of compound are removed. Now go back to STEP ONE and repeat the seating procedure using the last two of your new check valve balls. If all this doesn’t fix the problem, the pump will need to be removed from the engine and overhauled.