Thanks. I understand how those parts are laid out but do you think it is possible that the rotation of gears is somehow pushing oil into and filling up the trap door cavity somehow?
I know there are only two holes in the plate itself but doesn't oil pass though the bearings as well?

Just thinking, if oil is delivered into that cavity at a rate directly proportional to the revolutions/speed of the spinning gears, it could be forcing oil through the bearings, the trap door holes, filling the cavity, and thus forcing oil at pressure into the pushrod assembly?
I would think that the faster the gears spin, the greater the pressure into the cavity... which is why this issue really shows up at high RPM like you're verified.

I dunno. On-Paper reverse engineering...

EDIT: Take in mind that the counter shaft gear that is right up against the trapdoor is new, and contains an anti-rattle gear introduced this year.
Since that is the only change gear box side, wonder if that has anything to do with it.
I know it's straight-cut but could it somehow be feeding a bunch of oil into the trapdoor? Enough to raise the oil level at the mouth of the pushrod?

I'm still focused and mystified how oil is actually getting into the pushrod assembly...

 

The redline heavy is a 75-250 but flows like a 90wt oil according to Redline. I put the med in or light duty which is a 75-140 and I don't like it. I'm dropping it and will install the heavy back in, shifts like butter. LOL

 

You must live somewhere in the east? Many western states have 75mph and above speed limits. I believe Texas has some highways at 85mph. In Colorado I travel at 80mph regularly.

 

Anyone using Redline Shockproof HEAVY in their M8? If it's that thick maybe that's the answer to stop the transfer problem when running at 4K for 5 min. Seems like an easy test for someone with a Dyno

 

I have the advantage of owning several bikes so I am comparing the '14 with the '17 bikes side by side. The bearing in the '14 appears different than the one in the '17, I did not look the part number up for them. It could be the new anti backlash gear behind the bearing is causing the oil to come through the bearing more, I really do not know. All I do know is once I made the drain path larger it reduce the amount of transfer by well over half. So my next step is to find and get a sealed bearing to fit in place. This will stop all the oil from coming through the bearing into the pushrod area, then see what it does. This is just why I said I do not have a fix just a theory and so far its proving to be at least a part of it, maybe all of it.

 

While we can argue which holes for venting do what, I still believe that the core issues is the slip-assist clutch. It's pulling the oil that builds up around the clutch pushrod through mainshaft.. It may simply be drawing oil due to some motion parted on the rod or the flow of air imparted by the pressure plate.. Each cylinder really only generates force / torque during about 100 degrees of 360 (2 cylinders).. The SA clutch is clamping the clutch pack during that 100 degrees and relaxing for 260. This action is the source of the issue (my belief). What makes it happen on M8s and not TCs has to be something that is different between the bikes.. M8s make more torque. They likely clamp harder. As many have written, you can feel it in the clutch lever. Can you feel it in the clutch lever on a TC?

I mainly looked at the physical differences between the in the area of the tranny and primary. The physical construction of the venting system is different.. It becomes suspect.. At 4000 RPM there is a 67 Hz pulsation from the clutch that travels through the mainshaft. I suspect that it's somehow pulling oil from the tranny to the primary..

I plan on trying Darrel's vent mod but it takes time to see if anything has changed. The best way to test is to create a situation where the issue happens constantly and quickly and work from there. Have done that a bunch of times in the past.

Add:

From what I see being replaced, HD has no clue where the issue is..

 

Kinda makes sense at first but I don't think the clutch pack at speed tightens and then relaxes due to the weight of the bike on the belt countering forward motion, clutch inertia, and that heavy flywheel which does not relax due to inertia. I could be wrong but this is the reason you don't feel any pulses in the lever at 4K RPM etc, only at very low RPM and when you disengage the clutch.

Yes, so nothing has changed in reference to that side of the equation.

Hz indicates a wave so I would suspect unless there was a one way valve it would push and pull oil if that had anything to do with it. Not certain it would transfer anything otherwise.

I'm still with the theory that whatever forces the oil up to the level of the pushrod is the same force that is pushing oil down the pushrod. I believe whatever that force is.... grows with RPM.

 

Whoever came up with the gasket cut I have no idea but let's look at what it does. It enlarges the passageway from the main transmission cavity to the breather cavity which is vented to atmosphere. Now I've read here it's a 1/16" slot and the picture looks about 3/4" long give or take. So what it's done is vent more of the main cavity to atmosphere through the breather cavity. What I did was to vent the main case out directly to atmosphere through the fill hole (app 3/4"), both do the same thing only one is a much larger vent to atmosphere! For me it did nothing at all, other than make a mess when the cloth I had over it to catch fumes and mist came out of the way and allow oil mist to come out and onto the starter area that needed to be cleaned up.

Now for the pulsations, if its pulsing that would mean it pushes back and forth equally, right. If there was no oil at the pushrod area all it would do is move air back and forth. So lets get the oil out of the pushrod area and problem is solved. HD has made the pushrod area covered with a thin slot only to get in or out, I am sure to try and keep the oil out. The fact that its worked this way fine for years and continues to work on the twincam with the same clutch setup has to say something. I do not know if the new gear set is used in other application for '17 model year yet or if its a M8 only thing. I can say I've add a AEM lockup to my bike which pretty much stops the clutch from pulsing at higher RPM and it did not change the transfer rate at all.

 

It was me that said 1/16". I was just being sarcastic.

Like you've said, you may open that gasket hole as large as you want and air is still only going to be able to move through the restrictive tiny vent tube which it's rate will probably stay the same... low.
The test conducted with the open filler should trump that gasket mod 10 times over...

 

I believe Darren gave the credit for the slot idea to Herko. Regardless of the size of the slot, all the venting is done through a 3/16" hose. So to me, Amy hole oom the gasket larger than 3/16" isn't going to make a difference.
A simple, cheap test would be to vent the primary separately. This could easily be done worn drilling and tapping a small hole in a spare derby cover, a barbed fitting and a short price of hose. If it still transferred after that you coil at least rule out primary venting (or I should say lack of).