M8 trans fluid leaking in primary

[HogMike]

Well this tells me they H-D finally came out of the denial closet.

Maybe I missed it but I still haven't heard the factory explaining WHY this hose is needed and/or WHY the oil is moving.
??

[Jaycee1964]

Well this tells me they H-D finally came out of the denial closet.

Maybe I missed it but I still haven't heard the factory explaining WHY this hose is needed and/or WHY the oil is moving.
??

They realized the primary creates a Neg pressure AKA Vacuum .  The vent eliminates the Vacuum thus "Not" drawing fluid front the clutch shaft into the primary.

[Karl H.]

There is only one possible source for the vacuum in the primary imho: the crankcase. Most likely the press fittet spacer on which the crank shaft oil seal rides is not allways perfectly seated and airtight. A dealer here solved the problem by using a sealant between spacer and shaft (before the vent was released).

Karl

[kd]

There is only one possible source for the vacuum in the primary imho: the crankcase. Most likely the press fittet spacer on which the crank shaft oil seal rides is not allways perfectly seated and airtight. A dealer here solved the problem by using a sealant between spacer and shaft (before the vent was released).

Karl

I've always thought the sumping and transfer problem were related and the crankcase seal was the suspect (with K I S S methodology applied).  The seal makes sense but I have never had any opportunity to compare the M8 component fit so just followed the threads.  Several members here suggested using a gauge to track pressure changes but I never ever saw anyone do it and report their results.  Obviously the MOCO engineers did.!

[Sunny Jim]

There is only one possible source for the vacuum in the primary imho: the crankcase. Most likely the press fittet spacer on which the crank shaft oil seal rides is not allways perfectly seated and airtight. A dealer here solved the problem by using a sealant between spacer and shaft (before the vent was released).

Karl

Karl , can you elaborate please?
I, too, am beginning to think the Crankshaft seal may contribute to sumping. Given that this phenomenon has evolved over time( miles), there could be some truth in it. When I increased my displacement( after clocking up 6000 miles on same seal, bearings etc), the sumping was amplified dramatically. Considering there would be an increase in crank case pressure or vacuum, the seal may contribute.
The primary vent solves transfer but sumping remains.

[Karl H.]

I have no conclusive idea how transfer and sumping could have a common root. The improved crankcase venting system of the M8 might contribute to the vacuum build up in the primary but should not affect the oil flow from crankcase to oil tank imho. The air in the crankcase is linked to the air cavity of the oil tank. So both have no differential pressure which could influence the pumping performance of the oil pump.

Karl

[HogMike]

Well this tells me they H-D finally came out of the denial closet.

Maybe I missed it but I still haven't heard the factory explaining WHY this hose is needed and/or WHY the oil is moving.
??

They realized the primary creates a Neg pressure AKA Vacuum .  The vent eliminates the Vacuum thus "Not" drawing fluid front the clutch shaft into the primary.

I'm not too sure the "primary creates a Neg pressure "
I'm more inclined to believe what Karl noted about tracing the SOURCE of the vacuum to be the shaft seal.
I had talked to a factory tech who mentioned addressing that seal and trying different options to install a double lip seal, etc
The only way the primary can go to the vacuum state is when there is a vacuum applied to the primary. If the passage through the mainshaft is restricted (like with trans oil) the primary will suck the oil through the shaft before the passage is clear enough to let the negative pressure vent out the transmission vent as designed.
I see nothing either in the primary OR the trans that will make any pressure either negative or positive.
Just my 2cents

[Fat11Lo]

Just my opinion but I have been following these transfer/sumping discussions for quite a while now. As far as the transfer issue goes IMO if the trans oil did not have the chance to collect at the slave cylinder end it would not transfer to the primary. A vent's purpose is to let the compartment breathe positive or negative pressure in or out. The oil that collects at the slave cylinder end effectively seals off the primary's means of breathing. So far the most successful "fixes" have either let the oil drain from the slave cylinder area or let the primary breathe on its own. Either way prevents the trans oil from sealing off the slave cylinder end and transferring into the primary. Go back to high school physics air pressure in a confined space will increase or decrease proportionate to temperature. think about what it means to breathe, we draw air in and exhale it out. breathing is a two part motion so why wouldn't this same principal apply.

[Karl H.]

H-D has officialy explained that the rare transfer issues with the Twincam can be solved by a new crankshaft oil seal. So they committed that the negative crankcase pressure ist the source of the transfer problem with the Twincam. The design principles around the cranshaft seal are the same with the M8. I'm sure that the press fitted spacer combined with the higher negative crankcase pressure (better M8 venting system) and manufacturing tolerances can lead to an air leak between crankshaft and spacer. A dealer here successfully stopped the transfer on several bikes by sealing the gap.

Karl

[PoorUB]

Maybe I am crazy, but stopping the vacuum leak between the engine and primary seems like a better idea than just adding a breather on the primary, and allowing the leak to continue.

[road-dawgs1]

So I had the vent installed on my 19 at 500 miles. I did the 1k service myself at about 1400 miles. Now at 2k miles I just checked the tranny fluid and the stick is dry. I just double checked my receipt for the warranty work and only see the vent kit and 1 qt of syn3 listed on the parts used. Correct me if I'm wrong, but being a 19 I believe it should have had the deflector installed which is supposed to be removed (at minimum, checked to see if it's there). If they indeed had checked to verify and/or had removed it, wouldn't there be exhaust gaskets and tranny side cover gasket listed on the parts list? I read that leaving the oil deflector installed with the vent could cause the transfer to continue. I'm headed out Tuesday for a 4K mile trip and was hoping to not have to worry about this crap.

[Dmerch]

Have you reached around the back side of the primary to make sure the vent tube is actually there?

[road-dawgs1]

Have you reached around the back side of the primary to make sure the vent tube is actually there?

It's there, I checked it out when I picked it up.

[Dmerch]

Ok, then I got nothing...

[HogMike]

So I had the vent installed on my 19 at 500 miles. I did the 1k service myself at about 1400 miles. Now at 2k miles I just checked the tranny fluid and the stick is dry. I just double checked my receipt for the warranty work and only see the vent kit and 1 qt of syn3 listed on the parts used. Correct me if I'm wrong, but being a 19 I believe it should have had the deflector installed which is supposed to be removed (at minimum, checked to see if it's there). If they indeed had checked to verify and/or had removed it, wouldn't there be exhaust gaskets and tranny side cover gasket listed on the parts list? I read that leaving the oil deflector installed with the vent could cause the transfer to continue. I'm headed out Tuesday for a 4K mile trip and was hoping to not have to worry about this crap.

If it was me and leaving tomorrow I'd put some trans fluid in, blow through the new rubber tube to see if it's blocked, ride out and hit the next Harley dealer on your route and have them tell you "why" it's not working.
OR take it back to your dealer today and ask for a loaner bike.
Good luck

[road-dawgs1]

So I went to the dealer and bought a qt of gear lube to bring with me. While there I stopped into service and asked about not seeing any side cover gasket on the warranty parts list and asked if they indeed checked like the instructions advised to. After a round-about discussion regarding the existence of the oil deflector being a standard running change in the 19 model year that I won't get into here, they conceded and got me in and checked for the deflector.....low and behold it was still there. They removed it, buttoned it up and I was on my way. Im still bringing the gear lube (and 1 qt of engine oil) with me just in case. I'll be on my tomorrow morning with a little peace of mind.

[FSG]

well who'd of thunk it   

just as well you knew what the Service Bulletin was all about   

enjoy the trip      

[kd]

H-D has officialy explained that the rare transfer issues with the Twincam can be solved by a new crankshaft oil seal. So they committed that the negative crankcase pressure ist the source of the transfer problem with the Twincam. The design principles around the cranshaft seal are the same with the M8. I'm sure that the press fitted spacer combined with the higher negative crankcase pressure (better M8 venting system) and manufacturing tolerances can lead to an air leak between crankshaft and spacer. A dealer here successfully stopped the transfer on several bikes by sealing the gap.

Karl

Confirmation that they "say" it's the seal.  Why then doesn't the softail transfer?  Different seal assembly or crankcase volume ?

[Karl H.]

H-D has officialy explained that the rare transfer issues with the Twincam can be solved by a new crankshaft oil seal. So they committed that the negative crankcase pressure ist the source of the transfer problem with the Twincam. The design principles around the cranshaft seal are the same with the M8. I'm sure that the press fitted spacer combined with the higher negative crankcase pressure (better M8 venting system) and manufacturing tolerances can lead to an air leak between crankshaft and spacer. A dealer here successfully stopped the transfer on several bikes by sealing the gap.

Karl

Confirmation that they "say" it's the seal.  Why then doesn't the softail transfer?  Different seal assembly or crankcase volume ?

Tranfer can only occur with the hydraulic clutch actuator where enough oil is provided at the tranny side of the mainshaft.

[rigidthumper]

Did they

So I went to the dealer and bought a qt of gear lube to bring with me. While there I stopped into service and asked about not seeing any side cover gasket on the warranty parts list and asked if they indeed checked like the instructions advised to. After a round-about discussion regarding the existence of the oil deflector being a standard running change in the 19 model year that I won't get into here, they conceded and got me in and checked for the deflector.....low and behold it was still there. They removed it, buttoned it up and I was on my way. Im still bringing the gear lube (and 1 qt of engine oil) with me just in case. I'll be on my tomorrow morning with a little peace of mind.

Did they check/set fluid levels in both the trans and primary, too?

[Sunny Jim]

Here we go again.
Has anyone put a vacuum gauge on a primary vent?

[shysterorange]

Wouldn't a good crankcase vent, eliminate the negative primary pressure which is drawing tranny oil? Feuling or A1?

[PFWiz]

Had the vent mod installed under warranty on my 2018 CVO Limited 3 weeks ago after discovering my tranny dipstick was dry. Just got back from a 4800 mile ride and it appears that my transfer issue has been solved.

[PoorUB]

But having a slight vacuum in the engine crankcase is a good thing.

I still wonder why not fix the leak between the engine and primary?

[klammer76]

So I went to the dealer and bought a qt of gear lube to bring with me. While there I stopped into service and asked about not seeing any side cover gasket on the warranty parts list and asked if they indeed checked like the instructions advised to. After a round-about discussion regarding the existence of the oil deflector being a standard running change in the 19 model year that I won't get into here, they conceded and got me in and checked for the deflector.....low and behold it was still there. They removed it, buttoned it up and I was on my way. Im still bringing the gear lube (and 1 qt of engine oil) with me just in case. I'll be on my tomorrow morning with a little peace of mind.

Unbelievable what some of these dealerships do. I swear, most of the old time actual mechanics are gone, just kids bolting on parts nowadays.