A little more on the subject-

To dig a little deeper into this subject-

I know that these engines are sump and tank systems. Some even post that you could hook up a 55 gallon drum of oil to the bike and there would be no problem, arguing that oil level in the tank is irrelevant to blow-by.

I understand that theory, however, I also know that it does not work out that way in the reality of riding.

AND, Harley knows that too. That is why they put in large bold all CAPS print. CAUTION "Do not overfill the oil tank. Doing so can result in oil carryover to the air cleaner leading to equipment damage and/or equipment malfunction."

There is a direct relationship between blow-by and how much oil is in the tank.

As far as reduced amount of oil splashing around in the top end when the oil level is at mid-point or lower (but above the lower arrow), I do not believe this to be true for the following 2 reasons:

1. I have never observed a difference in oil pressure except when the oil is BELOW the bottom arrow, or above the top arrow. If it is at 1/3 above the bottom arrow, there is just as much oil pressure as when it is right below the top arrow. With no drop in oil pressure, it is hard to conceive how there would be less oil in the top end.

2. If there was less oil in the top end than needed, then Harley would be doing warranty work directly as a result of them saying to put the oil in the middle of the dip stick. I don't think they would recommend an oil level that would cost them money.

There IS one theoretical reason to run it all the way to the top line (when the engine is hot), and that is that you have about an extra 1/3-1/2 quart of oil that might reduce engine temps by 2-5* or so.

Bottom line- The tank has enough oil to fully lubricate the engine if the level is anywhere above the bottom arrow. So says HD and experience.

If the oil is above the top line when hot, or above the midway mark when cold, HD says this is OVERFULL and will cause excessive blow-by leading to equipment damage or malfunction.

 

And yet so many, many folks continue to run the incorrect weight oil as well as 2nd party air cleaners that don't breath correctly. Evidently the mechanics at the dealerships don't fully comprehend the manual either because they continue to recommend and install 20-50 synthetics in the hot climates. The idea of squirting in 20-50 synthetic in all 3 holes seems appealing to the service departments instead of actually reading the manual. It is not that 20-50 synthetic is going to grenade your engine but more to the point there are other oils which are better suited for hot climates.

 

Amazing isn't it!?!

 

Funny how this is brought up, I was just thinking about running 60wt in the summer here in Phoenix. I usually run 20-50 all year but thought it may be better to change when temps hit 100. May is when it starts to get hot and continues till late September.So I would change oil about every 6 months. What do you think about running redline 10w-60 or just straight 60wt?

 

Ok, you say Harley says not to fill your oil tank to the full level, because that extra 1/2 qt causes carryover. So how does it not happen by using this?., http://www.harley-davidson.com/store...pacity-oil-pan

 

I don't have any experience with that. However, HD recommends straight 50 over 20-50, so it makes sense that when they recommend straight 60 that the straight 60 would be better than 10-60.

That said, you are not going to do any damage running the redline 10-60, but will probably get more carry-over (blow-by) with the 10-60 vs straight 60.

You don't need to trust me that this is what Harley says, just read your owners manual.

The high-cap oil pan has more space for the extra 1.5 quart...my guess is that since it is all about crankcase pressure, it is pressure neutral to add space for 1.5 quarts and add 1.5 quarts of oil.

 

It is important to remember that the Harley manuals say to put 3 1/2 quarts of fresh oil into the 4 quart crankcase when initially refilling. Once that is done you would take the bike out and ride it to the point where it comes up to normal operating temperature. That would presumably be in the 210-230 degree area. Then ride the bike back to your shop and pull the dip stick to see where the oil is registering on the graduated scale. As the oil goes from cold to hot it expands, as do many liquids. So the hot level it is going to be higher up on the dipstick when it is at operating temp than when you originally put the initial 3 1/2 quarts in, when it was cold. It is from this hot level that you add new oil until it reaches the correct level on the dipstick. On my 96" the oil level drops about 1 dot on the dipstick when it cools off. When it gets up to normal operating temperature, it raises back up 1 dot to the correct (full) level on the stick.

I have a Screaming Eagle high volume air cleaner which does have the correct crankcase ventilation. I ride in 100 plus weather 4 or 5 months of the year and I don't have puking problems. I run a straight 60 weight oil when the ambient air temp stays over 80 degrees, as the manual suggests. Like has been enumerated several time earlier, running 20-50 weight will not blow your engine but at extreme temps of 80+ degrees ambient, a straight 60 weight would be better suited. Less potential for blow by has been cited as one reason.
This is all spelled out in our owner's manuals but you have to read it very carefully due to the fact that lawyers have written it in a very ambiguous style.

 

By putting 3 1/2 qts of oil in your motor when changing , and with what's left in the motor that won't drain out, a 1/2 qt isn't unreasonable and should give you a total of about 4 qts to lube the motor. And even if you do put 4 qts in it shouldn't come out the breather. The oil in your tank constantly circulates when the motor is running. It doesn't collect 4 qts in the top of the motor, then drain back into the oil tank. Which on most touring bikes is lower then the air cleaner. I believe its just a bad design that allows oil to dribble into the air cleaner and collect in the bottom of the filter. And after a while the filter is so saturated it just drips out onto the motor or even better blows all over your leg and the rest of the bike. The moco can claim anything the like and usally do, but this is a case of gravity doing its thing and the moco can't figure out a better way to do it. Heck they probably make more selling $600 oil pans then they would solving a known problem. In a way they never actually stopped dumping oil on the road like the EPA wanted them to, just did a smoke and mirror act to get them off their back.,,

 

I have a stroked evo (4.625") that creates a lot of crankcase pressure. So much so that it would blow past the dowel pin "O" rings. I replaced them so many times and tried many different remedy's that all failed. Then...I installed a vacuum pump where the smog bottle was, in front of the rear wheel. (1995 FLHR, under battery box) I wired it so it would not run unless the motor was running. Ran a hose from the breather bolts, to the pump, then out, down the side and exit under the rear fender at the tip. I added a small crankcase breather there also, because it would trip a few drops from the hose when parked. Now it is perfect.

 

The manual is a bit confusing. It does say to dump in 3.5 quarts when doing an oil change on a Twin Cam.

BUT it ALSO says that anytime the oil level is above the bottom mark no adding of oil is needed.

It ALSO says that you should NOT overfill it. Doing so can result in oil carryover.

I have changed oil on dozens of Twin Cams. The oil is hot when drained and filter removed. If I were to put 3.5 quarts in, most of them would be OVER the top mark on the dipstick when hot.

It ALSO says to use the correct weight oil for the temps the bike is being ridden in.

It is VERY RARE when running the correct weight oil AND have the oil level between the bottom and top marks for a bike to have any significant oil carryover.

It is VERY common for bikes to have significant oil carryover when using the incorrect weight oil and/or oil levels above the midway point on the dipstick when cold.