After studying the oil flow on the HD engine and knowing a little about pump laws, flows and headloss. I cannot understand why a slightly over full oil pan could cause oil to come out of the crank case breather and puke oil over the side of the bike. The pan is just a reservoir for the oil pump so the oil flow in the engine would only change by a very very small amount with the increase in level causing an increased suction head, but probably not at all since the oil pump is a PD pump. Oil out the breather would seem to be caused by inadequate draining of the upper regions of the engine. So someone tell me why my thought process is flawed, just asking. I know you guys are capable, my wife tells me everyday my thought process is flawed.

I don't have the problem and never have and I have slightly overfilled the tank at times, never by more than a 1/2 quart.

 

1. the oil flow in the engine does not change with an increase in the oil level.

2. Oil out the breather is not caused by inadequate draining of the top end. The top end drains oil at the same rate (all things being equal) regardless of the amount of oil in the system.

If you add oil to the oil tank, assuming that is was previously filled to approximately the correct amount, there will be no change in the flow of oil thru the system. There will be just more oil going thru it. It will be at a higher level in the oil pan and in other places where it is not already at maximum capacity such as the oil tank.

 

The bottom end of the engine is a dry sump configuration...there should be little to no puddling oil in the bottom end like in a car engine where the crankshaft slops around in the oil.
The hd oil pump not only pumps but scavenges oil from the bottom end (where it collects) and sends it back to the Oil TANK. If the tank is full or over full this limits the ability of the oil pump to scavenge because it has no place to send the oil back to (oil tank full or over full). The pump is constantly pumping but cannot scavenge it back to a full container. Thus the build up of oil in the top end or wherever. The pressure caused by the rotating assembly in the bottom end builds pressure and the pressure is released via the check valves in the heads which eventually vent to the breather passages and then to the air intake. If oil is allowed to accumulate in the heads (rocker boxes) because of the above reason then when the check valves release pressure it will send the accumulated oil with it.
Thus blow oil out through the air cleaner where the passages lead to.
This can also occur on older models where there is an external rubber oil line and that line becomes crimped or damaged limiting the scavenging of the oil pump trying to send the oil back to the tank.

A lot to write but I hope this helps.

 

I have posted this same stuff in the Sportster section.Sportsters are plagued with the problem worse than the other Harleys.By putting in a oil pump from a Buell which handles more oil flow,the oil out the breather or carb mouth is eliminated.

 

Thanks for the replies. Seems newer bikes with better pumps should not experience this as much.

 

I started this thread a week ago. It refers to '07-'10 touring bikes only.
https://www.hdforums.com/forum/touri...carryover.html
In that article it said. H D engineers have determined that overfilled engine oil causes: crankcase pressure to build up in the oil pan and crankcase pressure in the cam chest area remain lower, the vent line port in the oil pan to become covered in oil, which can then push oil into the cam chest area, causing the cam chest to overfill. Excessive oil iln the cam chest area won't register on the oil level dipstick. Oil left in the cam chest area won't return to the pan even when idling. Operating the engine with incorrect oil levels can cause permanent damage.
This info was from an article I read from a HD quarterly flyer my local dealer sends to me.