Okay, I'm willing to risk the beating I will take for asking this question. I'm trying to understand the whole notion of a dry sump, i.e. my ultra has an oil tank. When I change oil, I drain from the plug on the oil pan (the sump). If the oil that drains is not stored in the sump and the engine is not running, how does it get to the oil pan to drain? I have been through my shop manual and even searched for online diagrams of oil flow for a 2016 Ultra. Be kind with your sarcasm, please.

 

In a nut shell, the oil pump is two rotors side by side.
One is the pressure pulling from the oil bag under the transmission. On older Softails under the seat surrounding the battery. Also older Softails run a constant replace 1 1/2" or so oil in crank case since a lip retains a level. This splash lubrication lubricate inner cam bearings.

Oil from pressure side is driven thru a filter and thru engine. It mostly ends up in the crank case. At the bottom of the crank case is a return hole for the other oil pump return rotor. It is approximately 15% bigger. It pulls the dumped oil out and returns it to the oil bag.

The oil pump is mounted to a cam plate and is driven by the crank. There is a pressure release that maintains apx 35 psi max at high rpm.

Note the oil pump is located in cam galley outside crank case. Oil ending up here fills up the galley side and spills thru the main crank bearings over into the crank case.

Old EVO have oil pump on outside of motor. Also strangely, pump oil thru engine before oil filter. The return side of pump pushes oil back thru filter to oil bag.

The design of pump, filter and oil W (thickness) and the small engine size does not need a lot of oil at idle and also so it does not push thru two cooling oil injectors in crank case just under pistons. They are set to release at 18. So idle pressure is apx 10-12. That keeps from cooking oil at a red light.

The top end oil goes thru lifters up thru pushrod covers. It drains back into crank case thur a hole that goes down thru the cylinder.

 

The sump is where the crankshaft is spinning. If you were to pull that drain you would only get a few ounces of oil, hence the term dry sump. The oil you are draining is in a separate storage tank under the transmission on your touring bike. the suction side of the oil pump sends it there.

 

Thanks, great info

 

why you want to be sure to idle upright for a couple of minutes after getting oil to operating temp, before doing an oil change, to scavenge as much old dirty oil as possible back to the oil tank

 

Does this mean it makes sense to crank the engine after I drain it to fully expunge oil from the pan? Thanks for the information.

 

Don't do that. There is a little oil trapped in numerous places but it is basically just stained. No biggie.

It's all filtered. New oil will refresh it. It not really going to hurt anything and I seriously don't think you will see anymore coming out. The biggest trapped amount is in the cam galley and under valve covers.

On a TCb Softtail, there is about 20 oz or so in crank case.

If you try it, you just may drain down the lifters. Remember, they bleed since they can't overpower the valve springs. So cranking without oil in oil bag replacing lifter oil, they will collapse about 0.200. So when you start it, it will take about a good minute to pump back up to no clearance.

Not sure if you have heard what it sounds like that. Just find a heavy cast iron skillet. Now take a small hammer (preferably ball peen) and tap the skillet pretty hard and fast.

It's interesting how many people talk about lifter noise when it really is just the pistons rocking as they pass the bottom of the stroke.

You will truly think it's going to blow up.

Sure this thread will go to the tin men that sell engine purges. So be it. If you truly need to fill the oil needs totally done, use one of those.

 

Rip, you’re reading my mind. I’ve thought about the scavenger product but will probably opt for an oil flush with cheap oil and add the good stuff after I drain the cheap flush

 

Just remember, you're leaving a quart almost of what you throw in there last time.

 

Although I don’t have statistics, I really doubt there are many oil or oil change related engine failures. You are correct, you are not changing all the oil out with an oil change. Just stick to a regularly scheduled oil change intervals and you’ll be fine. I wouldn’t waste time flushing with a cheap oil, never good to mix different brands of oil. You could always send your old oil in for an analysis to see how it’s performing.