M8 trans fluid leaking in primary

[Pete_Vit]

These latest reports are encouraging, as mine still hasn't moved with the modified gasket.

400 plus miles and a complete dyno tune with 30 plus max power runs, with more dyno time coming very soon.

[Sunny Jim]

A fella on M8 owners FB page has had this issue. His dealer has diagnosed a faulty crankshaft seal and plate . It allegedly causes a vacuum in the primary causing the oil transfer from trans. His dealer insists this is the cure!
Go figure!?!?

[harleytuner]

A fella on M8 owners FB page has had this issue. His dealer has diagnosed a faulty crankshaft seal and plate . It allegedly causes a vacuum in the primary causing the oil transfer from trans. His dealer insists this is the cure!
Go figure!?!?

I wonder whee the vacuum would be coming from  as there is no suction on the bteathers

[HV]

ANy bad Crank Seals Ive seen transferred Engine oil IN to the Primary 

[1FSTRK]

I see they have a new part number on the sprocket shaft seal, is it a double spring two way seal like the twin cam or did they go back to a single spring seal like the Evo?

[rbabos]

The function of the breather valves is to create a low pressure in the case. The outflow from breathers on piston down stroke is what you feel at the nipples. On the up stroke there is a slight negative pressure . This is very noticable when engine is first started. With the blowby from the cyls, generally it ends up being somewhat static in the case. When you decel there is negative pressure on top of the pistons and again there will be a low pressure in the case. Entirely possible a seal can cause transfer from the trans but it will be happening on decels. Now if these fools actually used a single lip seal in the first place, well, . It would be directional in oil control. It needs control in both directions for breather function. Much like seals in a two stroke engine.  If a standard seal out and out fails , engine oil will transfer to the primary being the crank is the high point. Air would also be going both ways past the seal on pistion up and downs so it would cancel out any chance to build negative pressure in the primary.
Ron

[HD/Wrench]

seal on the ones I have built are double lip it that matters . Never seen one engine pull oil in.. So let me get this straight its creating a vacuum through the primary and thus into the trans ,  but its not pulling the level of the primary down thats funny so its a selective one way valve  Sorry but if its pulling on that area it would keep pulling and raise the level of the engine oil as well . 

[Sunny Jim]

I tend to agree with GMR.

[harleytuner]

seal on the ones I have built are double lip it that matters . Never seen one engine pull oil in.. So let me get this straight its creating a vacuum through the primary and thus into the trans ,  but its not pulling the level of the primary down thats funny so its a selective one way valve  Sorry but if its pulling on that area it would keep pulling and raise the level of the engine oil as well .

Pretty much what I was getting at.  I know of one stock bike that had the main seal replaced then ridden hard for 20 miles or so and it was still sumping.  At this point I don't think they have a clue of how to fix some of the issues they have. You have to know the cause to figure out the fix. 

[rbabos]

seal on the ones I have built are double lip it that matters . Never seen one engine pull oil in.. So let me get this straight its creating a vacuum through the primary and thus into the trans ,  but its not pulling the level of the primary down thats funny so its a selective one way valve  Sorry but if its pulling on that area it would keep pulling and raise the level of the engine oil as well .

You can't pull fluid out of the primary because the level is quite a bit below the crank and seal, right? We both know there's next to no oil around the seal area from primary fluid. If there's already a revision on the seal, that means they fkd up somehow. It is after all a simple seal but one or two lips makes a difference if in fact the early ones came with a single lip. Who knows, but yes a single lip will act like a one way valve with umbrellas in play in the breather system.
Ron

[1FSTRK]

seal on the ones I have built are double lip it that matters . Never seen one engine pull oil in.. So let me get this straight its creating a vacuum through the primary and thus into the trans ,  but its not pulling the level of the primary down thats funny so its a selective one way valve  Sorry but if its pulling on that area it would keep pulling and raise the level of the engine oil as well .

You can't pull fluid out of the primary because the level is quite a bit below the crank and seal, right? We both know there's next to no oil around the seal area from primary fluid. If there's already a revision on the seal, that means they fkd up somehow. It is after all a simple seal but one or two lips makes a difference if in fact the early ones came with a single lip. Who knows, but yes a single lip will act like a one way valve with umbrellas in play in the breather system.
Ron

I agree there is little or no primary oil in the area around the engine sprocket shaft seal so no oil transfer to the crank case would not surprise me. There is a big difference between a single spring double lip seal like the shovels and evos used and the two way double spring seals used in the twin cams so if the M-8 went back to the single spring double lip there could very easily be an air transfer. They make a big deal about the M-8's new improved breather system and if indeed it works and the guy actually did a good breakin so the rings seal you could easily get some crank case vacuum, they would evacuate about 107ci of air on every down stroke and the only way to refill the case cavity is if you have blow by.

[Sunny Jim]

Ok so if this is the case, how does Darren's mod to trans cover gasket weigh in to the debate?

[1FSTRK]

Ok so if this is the case, how does Darren's mod to trans cover gasket weigh in to the debate?

I am only saying that this to is plausible. I do not think anyone has a real handle on the cause and without a true root cause many things may effect what is happening but a true cure will not come.

[Bike31]

If there's a vacuum and a leak there's a source to fill it. Maybe someone should put a gauge on the transmission breather and see what the vacuum/pressure changes are at various rpms?

Gary

[1FSTRK]

If there's a vacuum and a leak there's a source to fill it. Maybe someone should put a gauge on the transmission breather and see what the vacuum/pressure changes are at various rpms?

Gary

Good idea, I bet you could leave the trans vent open, hook a vacuum/boost sensor to the primary and gragh the pressure right on the dyno during multiple runs just like you do to test air cleaner pressure.

[Bobv]

If there's a vacuum and a leak there's a source to fill it. Maybe someone should put a gauge on the transmission breather and see what the vacuum/pressure changes are at various rpms?

Gary

That has been my thought for quite some time. Doesn't seem like it would be real difficult but might provide some answers or at least rule that out.

[rbabos]

I find this all interesting. Discussions are great but seldom solve issues.  Me, I'd whip up a fitting for the primary some way and attach a vacuum gauge it to the primary and see if it pulls vacuum on hard decels or above 3500 rpms. Great test for any dyno tuners here. Should be done on a hot primay, where out venting will have already slowed from expansion.  It might also be possible to attach the gauge to the trans vent to see the same but this would be a much lower reading, I think since oil transfer within the main shaft would reduce the effect or slow it down so it could be seen. Primary would show it better. Testing will either rule it out or confirm a possible seal problem. It's entirely possible there are two issues in play here. An over abundance of oil around the main shaft hole for he pushrod and primary suction pulling gear oil from the box to the primary.
Ron

[harleytuner]

I find this all interesting. Discussions are great but seldom solve issues.  Me, I'd whip up a fitting for the primary some way and attach a vacuum gauge it to the primary and see if it pulls vacuum on hard decels or above 3500 rpms. Great test for any dyno tuners here. Should be done on a hot primay, where out venting will have already slowed from expansion.  It might also be possible to attach the gauge to the trans vent to see the same but this would be a much lower reading, I think since oil transfer within the main shaft would reduce the effect or slow it down so it could be seen. Primary would show it better. Testing will either rule it out or confirm a possible seal problem. It's entirely possible there are two issues in play here. An over abundance of oil around the main shaft hole for he pushrod and primary suction pulling gear oil from the box to the primary.
Ron

I'm supposed to have a stage IV 114 coming in for a tune.  If he shows i'll try to find the time to test the vacuum on just the primary.  Just depends on how much time I have to mess with it and if someone is around to video the vacuum gauge while I rune the bike.  Really simple to do but i'm still messed up with this hip, so even the simple things can be a PITA.  I can test both the M* and a TC very easily. 

[rbabos]

I find this all interesting. Discussions are great but seldom solve issues.  Me, I'd whip up a fitting for the primary some way and attach a vacuum gauge it to the primary and see if it pulls vacuum on hard decels or above 3500 rpms. Great test for any dyno tuners here. Should be done on a hot primay, where out venting will have already slowed from expansion.  It might also be possible to attach the gauge to the trans vent to see the same but this would be a much lower reading, I think since oil transfer within the main shaft would reduce the effect or slow it down so it could be seen. Primary would show it better. Testing will either rule it out or confirm a possible seal problem. It's entirely possible there are two issues in play here. An over abundance of oil around the main shaft hole for he pushrod and primary suction pulling gear oil from the box to the primary.
Ron

I'm supposed to have a stage IV 114 coming in for a tune.  If he shows i'll try to find the time to test the vacuum on just the primary.  Just depends on how much time I have to mess with it and if someone is around to video the vacuum gauge while I rune the bike.  Really simple to do but i'm still messed up with this hip, so even the simple things can be a PITA.  I can test both the M* and a TC very easily.

I think it's worth a shot when you are up to it. It would have to be a known bike that does transfer from gearbox to primary. If at some point they might have changed the seal mid production so it might not show up in testing. Seems some do and some don't transfer oil. The seal could be ruled out or confirmed in testing on one that has the issue.
Ron

[harleytuner]

I find this all interesting. Discussions are great but seldom solve issues.  Me, I'd whip up a fitting for the primary some way and attach a vacuum gauge it to the primary and see if it pulls vacuum on hard decels or above 3500 rpms. Great test for any dyno tuners here. Should be done on a hot primay, where out venting will have already slowed from expansion.  It might also be possible to attach the gauge to the trans vent to see the same but this would be a much lower reading, I think since oil transfer within the main shaft would reduce the effect or slow it down so it could be seen. Primary would show it better. Testing will either rule it out or confirm a possible seal problem. It's entirely possible there are two issues in play here. An over abundance of oil around the main shaft hole for he pushrod and primary suction pulling gear oil from the box to the primary.
Ron

I'm supposed to have a stage IV 114 coming in for a tune.  If he shows i'll try to find the time to test the vacuum on just the primary.  Just depends on how much time I have to mess with it and if someone is around to video the vacuum gauge while I rune the bike.  Really simple to do but i'm still messed up with this hip, so even the simple things can be a PITA.  I can test both the M* and a TC very easily.

I think it's worth a shot when you are up to it. It would have to be a known bike that does transfer from gearbox to primary. If at some point they might have changed the seal mid production so it might not show up in testing. Seems some do and some don't transfer oil. The seal could be ruled out or confirmed in testing on one that has the issue.
Ron

I agree but i'll run the test weather or not it's transferring.  If it's not it will give a baseline off a known good one to compare to the next bad one. 

[les]

A fella on M8 owners FB page has had this issue. His dealer has diagnosed a faulty crankshaft seal and plate . It allegedly causes a vacuum in the primary causing the oil transfer from trans. His dealer insists this is the cure!
Go figure!?!?

What is a crankshaft plate?

[Sunny Jim]

Would a vacuum gauge in the trans breather be appropriate?

[rbabos]

Would a vacuum gauge in the trans breather be appropriate?

Might not react fast enough . Oil being drawn in, if it actually is past the pushrod will act like a seal to the trans slowing the vacuum effect on the trans side. Primary will react instantly to vacuum if present. I would think mostly at decel conditions where the case is at it's most negative pressure. All this of course if it's main seal related. Yet to be tested and proven.
Ron

[Sunny Jim]

Yes on HD forum - M8 section , the discussion bubbling away. Mr Cole believes it's a tranny issue. I think Max concurs.

[rbabos]

Yes on HD forum - M8 section , the discussion bubbling away. Mr Cole believes it's a tranny issue. I think Max concurs.

OOOH. In that case I better crawl under a rock then with my far fetched ideas. Pretty sure the members here can find the cause sooner then the chrome whore site. The game is afoot, so they say.
Ron