I applied indelible black marker and its much easier to read.

Thanks to whoever suggested such.

 

I find that using the LED light on my iPhone works just fine for seeing the fluid on the dipstick. I use the passenger foot board as a shelf with the phone hanging over.

 

So it appears that there 'may' be an official cure. I entered ' Milwaukee 8 owners' on Facebook and stumbled across an owner who has had the oil transfer fault. The MoCo is recommending to replace the crank seal. Aporently this seal issue is creating a vacuum in the primary, thus drawing oil from the gearbox. I am not convinced, however discussions on Harley Tech Talk suggest that this could be feasible. I would really appreciate Steve Coles input on this one. Watch this space.

 

I talked to steve last night about it, I'll let him fill you in lol. Back to the drawing board HD.

 

I do not think it will be a fix but you never know. Here is the issue as I see it. Let's assume there is a vacuum through the seal as they claim, why is it not drawing oil from the primary into the engine? Each time I have had transfer I can always find all the oil missing from the transmission in the primary and my oil level for the engine has never gone up any, just down some. The primary level rises to a point well above the crankshaft seal so no issue sucking it into the engine. Second problem I see is where is this so called vacuum coming from, the engine breather will not allow it and typically we all find oil in the air cleaner assemble which means the engine is push it out and that means there is pressure in the crankcase not a vacuum! Like I said before KISS first and this theroy does not pass the BS meter in my book.

 

The breathers vent positive crankcase pressure and retain negative crankcase pressure. They are one way valves.
Whenever the pistons go up you have negative pressure in the case. You can watch this alteration in pressure by putting a piece of paper over the open oil filler tube.

Not sure the oil in the primary goes as far up as the crank in level. Most of it is usually collected around the outside perimeter of the primary case, or down in the clutch valley.
Furthermore, any oil that managed to get past the comp, the crank adapter, springs, and rotor would most likely be spun off by centrifugal force before having a chance to be sucked into the engine.

I could be completely wrong, but sounds plausible.

 

Let's for a moment assume that it works like you think. Each time the cylinders come down the pressure would rise and the seal would leak, this is just why a bad crank seal pushes engine oil into the primary and it has done this for years on combustion engines. So where is our engine oil in the primary? Also you still have ring leakage no matter how good they are and a typical number range in the 3 -7 % on fresh M8 engines. So now as those pistons are heading up the bores towards top dead center you are loosing that possible vacuum. What you are feeling is the air moving around as the pistons move but I have never seen a vacuum in any engine unless and evacuation system is being employed. Mind you we do have to run something fairly large to draw a vacuum on and engine crankcase. It typically will add power when you can draw a vacuum but you have to run an external pump to get there.

If your theory about the primary oil is valid then it would also have to be valid in the transmission as the oil level is below the push-rod area too. The fact is the primary oil level will rise to above the crankshaft center-line and I have already seen/measured that. So if it was indeed true you would have no transmission transfer but we all know that is not the case. I wish this was a simple issue but it is not.

 

If there were a vacuum crankcase>primary>transmission would it be detectable at the transmission's breather? Install a gauge on the breather and see what's happening at rpm.

Gary

 

I dunno, I'm kinda with Harley on this one - plausible. Guess we'll find out eventually.

Couple of things. One, Yes, the pistons moving up and down is the primary cause of the positive and negative pressures in the case. Paper over the oil filler clearly shows that. In a sealed system the pressures would be opposite and equal. Positive, negative, positive, negative as the pistons go up and down. However, add in ring blowby and the positive cycle is now higher than the negative cycle and thus you have a need for positive crankcase ventilation. That's how all engines work. If you didn't have negative pressure when the pistons were up, and you let the case equalize, when they came down, you'd then have 1800CCs of air to move out of the breathers... Fact is, the system needs the negative pressure to enhance performance otherwise the pistons would have to fight significant high pressure as they came down. What comes out of the breathers is whatever was added by blowby plus some of the natural positive pressure which interestingly enough helps create more vacuum on the negative pressure stroke.

Harley knows there is negative pressure. Apparently they think their crank seal is weak (in one direction) and depending on how it's shaped, could be. Like you alluded to, we know these seals can in fact leak from positive pressures - aka, blocked breather tubes, so it's not a far stretch to imagine that if the seal was improperly designed, maybe the small negative pressures the case does see, maybe it's pulling air from the primary. They can obviously be wrong, but from a mechanical engineering standpoint, they might be on to something. I kinda wonder if this scenario could be the root of some of the other oiling issues they're having. Pumps need positive crankcase pressure... too much negative and you get feed issues.

Two, there was a video running around here that was made by of the aftermarket guys - they made a clear outer primary cover. In that video it shows that oil does not raise to the level of the crankshaft. If it did we wouldn't need an external oiler for the comp - which was what they were testing for. Remember all the issues with comp oiling? Oil starved comps? Both interior and external? Compusaver? In the video oil was clearly showed being spun around the primary case and not collecting at the crankshaft. Most of the oil fed back down into the clutch valley after painting the walls. So it's not my "theory". Makes sense too.

 

I'm not trying to speak for Steve, but i think he was saying his primary level got up to the mid point of the seal after the transmission fluid migrated into the primary. And if that's the case and a vacuum is being pulled from the engine case why didn't it pull primary/trans fluid into the engine.