I've examined my FSM, and it mentions nothing about any oil draining from the tank into the crankcase sump when bike is not operated.

Looking at the schematics and description of the oiling system, the feed line oil would have to (by gravity alone?) go through the lower gerotor and upwards into the filter mount. There it would either have to open the cold oil (high pressure) bypass or the checkball and spring inside the filter housing that opens between 4 and 6 pounds of pressure. Then it would have to travel through the oil galleries and return to the sump by some method.

It appears the return hose is above the oil level in the tank, so no siphoning on the return line, correct?

I find it hard to believe 2.5 quarts can generate that much pressure (by gravity alone?) while the engine is stopped. Obviously, your oil light comes on before you start the engine, so no oil pressure before engine is running, correct?

Can someone explain the physics or mechanics of this process? I find it hard to believe everyone's checkball is defective except mine. My bike has sat for weeks without any change of level in my oil tank.

I'm not saying it doesn't happen, just not sure of a logical explanation.

I'm also not talking about high speed sumping on the scavenge side of the pump, just this mysterious "leakdown" I keep reading about.

John

 

yes its a normal harley thing. when the oil cools down the ball spring gets stuck open. only remedy is to fire it up for a minute or two every couple of days.

 

I guess I have an abnormal Harley, because mine has never done it in 22 years of ownership.

John

 

your check valve spring is worn after 20 yrs or the ball is not seating to stop the oil completely. some people blow a quart out of thier vent after sitting for a while

 

John, my 2007 1200-C does not leak down, I tore my left bicep loose from my shoulder and 75% of the rotator cuff so my bike sat from November of 2011 until Sept 5th. It has 18,000 on it and so far no leak down. I use the big Harley 63813-90T and am now looking for something to use in its place as Harley has discontinued. I like to use the large one because you can three whole quarts with no worries.

 

Some times mine leaks down and some times it don't. I always check it hot so there isn't a problem.

 

Thanks to all, I guess I can understand how this happens. I still think it's odd that Harley has not found a solution in over 26 years of making the evo motor. What good is a check ball if it doesn't check sometimes?

John

 

Same here. My theory is it may depend in part on how the oil pump gears line up on shutting down.

Anyhow, think of the all the splash lubrication you are getting to the bottom end on cold startup churning extra sump oil after leakdown. Heck, maybe H-D even intended this as a design feature!

Cheers, RR