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Discussion Starter #1
a little something showed up in my inbox. A new fix from the MoCo to address oil carry over from the trans to the primary. As I understand it, its not as of yet released to the public. But if you have the issue under warranty you should be able to get it installed. But you might have to do some educating first, as not everyone will have the word yet.









 

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Wonder why these primaries are creating a low psi, drawing xmsn oil, vs prior big twin generations? Don't think my '03 wide glide primary is vented. Crankcase psi tied into the xmsn/primary M8 for epa reasons?
 

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Discussion Starter #5
Wonder why these primaries are creating a low psi, drawing xmsn oil, vs prior big twin generations? Don't think my '03 wide glide primary is vented. Crankcase psi tied into the xmsn/primary M8 for epa reasons?
Seems to me that to pull a meaningful amount of oil out of the trans, there would need to be suction on the primary. As in primary seal acting as a breather valve. And that would require a vacuum on the crankcase, which there could be on the upstroke if the ring seal was good, and there was no residual pressure left from the last down stroke. Which with just a little imagination connects us to the crankcase sumping issue.

I'll wait until someone says this cured their issue. Although it might be worth plumbing a vacuum gauge to the trans vent, just to see what is going on as far as pressures. And suction on the trans would be from the primary, and that would have to be from the motor itself.
 

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Seems to me that to pull a meaningful amount of oil out of the trans, there would need to be suction on the primary. As in primary seal acting as a breather valve. And that would require a vacuum on the crankcase, which there could be on the upstroke if the ring seal was good, and there was no residual pressure left from the last down stroke. Which with just a little imagination connects us to the crankcase sumping issue.

I'll wait until someone says this cured their issue. Although it might be worth plumbing a vacuum gauge to the trans vent, just to see what is going on as far as pressures. And suction on the trans would be from the primary, and that would have to be from the motor itself.
Would have to dig out the service manual to see how they plumbed the xmsn vent(to the crankcase?). Possibly the xmsn vent getting pressurized from the crankcase(down stroke), which in turn pushing xmsn oil to primary.
 

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It'll be interesting to see if the venting fix actually works. I still continue to believe that if they'd just unshroud the right side bearing so it's not continually swamped with oil (you know, like it used to be before '17 when this issue started?!), there'd be no way for migration to occur.
 

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I wonder if a crank vent from ET performance would relieve the crank case pressure enough to stop the oil transfer, if the crank case pressure is the cause.
 

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Discussion Starter #9
Would have to dig out the service manual to see how they plumbed the xmsn vent(to the crankcase?). Possibly the xmsn vent getting pressurized from the crankcase(down stroke), which in turn pushing xmsn oil to primary.
XMSN = Transmission?

The crank case vents through the vent valves into the breather.

The primary vents through the mainshaft to the trans, and the trans vents through the vent hose in the top cover.

Only difference on the M8 is the new vent valves. But its the same flapper valve in a package with a lot more oil control.



After thinking on it a while, I'm ready to dig out my old vacuum gauge and see if the is any sucking taking place on the trans. Because with out some sort of lower pressure in the primary pulling the fluid across, this kit is for naught. Just like the first fix, which was lefty seals in the motor.
 

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Discussion Starter #10
It'll be interesting to see if the venting fix actually works. I still continue to believe that if they'd just unshroud the right side bearing so it's not continually swamped with oil (you know, like it used to be before '17 when this issue started?!), there'd be no way for migration to occur.
That has been an area were the MoCo has been poking around. And there was a change to that bearing in 17.

If you look at the housing where the clutch slave sits, it would tend to pump the oil through with each lever release. ANd there have been at least two fixed tested on that area. Maybe they didn't work, or maybe they are just looking for a cheaper fix.

A for sure fix would be this vent and a seal on the pushrod like they used on the 4 speeds. Could be built into the clutch retention nut or it could be something that snapped over the nut.

4 speed push rod seal/nut
 

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Discussion Starter #11
I wonder if a crank vent from ET performance would relieve the crank case pressure enough to stop the oil transfer, if the crank case pressure is the cause.
That setup is mickey mouse. Just a rehash of the old top breather gizmos.

The top of the trans already has a passage down to the oil pan. Air cooled motors return oil through a tube installed there, and its just capped on wet heads.

If you want to vent the pan, then modifying one of the return tubes would be the way to go about it. Wet heads would just need a separation baffle and a hose added to a tube. Air heads would need a second tube to be added as the vent. The vent could run in through the side of the return tube.
 

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XMSN = Transmission?

The crank case vents through the vent valves into the breather.

The primary vents through the mainshaft to the trans, and the trans vents through the vent hose in the top cover.

Only difference on the M8 is the new vent valves. But its the same flapper valve in a package with a lot more oil control.



After thinking on it a while, I'm ready to dig out my old vacuum gauge and see if the is any sucking taking place on the trans. Because with out some sort of lower pressure in the primary pulling the fluid across, this kit is for naught. Just like the first fix, which was lefty seals in the motor.
Sorry about that, work abbreviation, yes-transmission=xmsn. Appreciate the info and cut-away pic. Wonder if tolerances come into play with some not having the transfer issue yet. Any chance pressure is building on the right side of the clutch pushrod, causing transfer? You thinking of hooking a vacuum gauge to the transmission vent tube and seeing what going on during cruise and aggressive acceleration/deceleration?

I'm planning on using Mobil 1 75w90 or 75w140 gear oil in my transmission as I have in prior bikes on the next change( Dealer used Syn3 in all 3 holes at the included 1000mi service). I've noticed smoother/quieter shifting with it. Not sure if it will make a difference as far as the transfer issue though. Only have 1800 mi. on my RGS so far and no problems.
 

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because of Kevin Cameron's article about the "new" Milwaukee-8 i was under the impression that overfills were directed to the transmission.

"Small details are important. In the past, if the oil was overfilled, excess oil could wet the air filter via the breather. This has now been rerouted through the transmission case."

https://www.cycleworld.com/harley-davidson-motorcycles-new-milwaukee-eight-big-twin-engine#page-10

can't vouch for the validity of that statement, but for the sake of discussion, could an "overfill" situation pressurize the tranny, leading to the primary?

Also, if they vent to atmosphere, wouldn't that be "illegal" in Europa?

@Thermodyne do you have migration on your '18 RGU?

i just drained & filled mine and it was ok.
 

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Discussion Starter #14
because of Kevin Cameron's article about the "new" Milwaukee-8 i was under the impression that overfills were directed to the transmission.

Also, if they vent to atmosphere, wouldn't that be "illegal" in Europa?

@Thermodyne do you have migration on your '18 RGU?

i just drained & filled mine and it was ok.
No idea as to what the EU allows for on scooters.

Mine has not transferred as of yet. But it really has not had the opportunity, still working on the second thousand miles. Today was the first run on the big slab of more than a few miles. I'll keep Formula+ in the trans for now, just in case.

If you look at the changes that came in 17, you got a new trapdoor with the clutch cylinder sealed to it. So there could be drain issues and there could be pumping issues from the slave piston. On the other end you got a new clutch, and the hub fits closely onto a cylinder shaped area at the end of the main shaft, so there could be some pumping taking place there too. And when one side pushes, the other side would suck. The much larger area in the clutch cavity would make it less apt to pump fluid back to the trans.

When the MoCo first realized there was an issue, they kinda fell back on history. They went right after the lefty seal, which has been an issue in the past. Then they played around some on the trapdoor area, couple of test fixes, and now they are back fooling with suction in the primary. So I'm thinking its one of three things. 1) They have no idea as to the cause. 2) Its a perfect storm sort of thing where there are many issues and when a few of them end up on the same scooter, it transfers. 3) They know what the issue is and are looking for the cheapest fix that can be done in the field. With that in place, they can then quietly effect a redesign on production scooters without fear of getting forced into putting the production fix on scooters in the field. If it was say a redesigned trapdoor, that would cost an arm and a leg to do as a no cost campaign.
 

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My '19 RG has the migration issue. I checked the trans fluid level at delivery and at about 200 miles, it was in the middle of the add and full marks. Checked it again on Monday at 631 miles, nothing on the stick. It took 16 ozs to put it in the middle.
I rode 200 miles and checked it the next morning, down another 5 ozs.

So I pulled the derby cover and removed the excess. Then pulled the pushrod and modified it. Just trying the simplest fix first. If that doesn't help, I'll have to see if the MoCo's new vent tube is successful. If not, I'll modify the trans side cover to better drain the oil away from the bearing area.
 

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Mine has not transferred as of yet. But it really has not had the opportunity, still working on the second thousand miles. Today was the first run on the big slab of more than a few miles. I'll keep Formula+ in the trans for now, just in case.
thanks for your reply.

i am getting ready to turn over 10K on mine. mostly highway cruising, revs usually 2500-3500 in 6th.
i very rarely get to redline; power falls off so soon it's more enjoyable for me to short-shift and it sounds better, too.

so many upgrades to the ole pushrod v-twin!

we should really be glad they're still around instead of trying to make street rods out of 'em.
and the profitable aftermarket always seems to take up the slack for them anyway.

really looking forward to the results of your experimental testing!!!
 

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To the OP- this just showed up and they expect you to do that work to your bike? Are you/have you been working with them or is this random?

I wouldn’t think this should be something your avg joe should be doing in their garage if they aren’t mechanically savvy.
 

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OP, thanks for the info.

looks like this Harley kit 94100065 can’t be found when you google it.

So you have to drill to install this vent. I rather not do this, with MoCo’s track record, who know if they even tested this & what the long term effect is.
 
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