Originally Posted by jimcb1
(Post 18290655)
any one else see new bikes with vent installed from factory
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Originally Posted by Candler
(Post 18291252)
Adding the vent kit to to the primary case to eliminate any atmospheric pressure differentials and the success of said kit eliminating any fluid transfer from the trans case proves there is a vacuum of some level being created in the primary.
If the trans case was being pressurized and transferring fluid to the primary then the vent would not work. The trans would still transfer fluid. I think the vacuum is being created in the crankcase sucking air from the primary around the crankcase seal also possibly causing the sumping issue as the oil pump fights the negative pressure to scavenge the oil properly. |
To me that would imply that something in the crankcase ventilation system is holding vacuum in the crankcase instead of venting properly.
It is my understanding that the EPA mandated that crankcases can't be ventilated directly to outside air. Perhaps someone with more understanding of the M8 pcv system can chime in. |
Originally Posted by JayD6951
(Post 18291370)
Just came from the local dealer and checked it out. I found 2 out of 8 with the breather hose already installed from the factory. The ones with the breather hose had 5/19 build dates. It’s very discreet and hard to see unless you feel for it with your hand. I just ordered a kit and I’m installing it myself to avoid H-D’s charades.
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Originally Posted by Candler
(Post 18291490)
To me that would imply that something in the crankcase ventilation system is holding vacuum in the crankcase instead of venting properly.
It is my understanding that the EPA mandated that crankcases can't be ventilated directly to outside air. Perhaps someone with more understanding of the M8 pcv system can chime in. |
Originally Posted by BrandonSmith
(Post 18291696)
The crankcase is vented into the air cleaner. My understanding is that there isn't a pcv.
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Originally Posted by Candler
(Post 18291252)
Adding the vent kit to to the primary case to eliminate any atmospheric pressure differentials and the success of said kit eliminating any fluid transfer from the trans case proves there is a vacuum of some level being created in the primary.
If the trans case was being pressurized and transferring fluid to the primary then the vent would not work. The trans would still transfer fluid. I think the vacuum is being created in the crankcase sucking air from the primary around the crankcase seal also possibly causing the sumping issue as the oil pump fights the negative pressure to scavenge the oil properly. |
Originally Posted by JayD6951
(Post 18291370)
Just came from the local dealer and checked it out. I found 2 out of 8 with the breather hose already installed from the factory. The ones with the breather hose had 5/19 build dates. It’s very discreet and hard to see unless you feel for it with your hand. I just ordered a kit and I’m installing it myself to avoid H-D’s charades.
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Originally Posted by KrustyKush
(Post 18291414)
I'm not educated about engine internals, but a naive question: A low pressure on the crank seal caused by pistons rising. Wouldn't there also be a high pressure caused by pistons falling?
1. If the primary is sealed off completely from the transmission and the atmosphere, a very minuscule amount of air would pass through the seal into the crankcase to balance the pressure between the crankcase and primary. 2 .If the primary is sealed off only to the atmosphere and was open to the transmission (i.e. a sloppy tolerance between the clutch pushrod and its passage), the air that was just sucked from the primary has to be replaced, which would come through the clutch pushrod passage, bringing with it transmission fluid. 3. If the primary is sealed off only to the transmission and was open to the atmosphere (i.e. a tight clearance between the clutch pushrod and its passage, and with a primary vent installed), the the air that was just sucked from the primary has to be replaced, which would come from the atmosphere. 4. If the primary is open to both the atmosphere and transmission (i.e. a sloppy tolerance between the clutch pushrod and its passage, and a primary vent installed), the air that was just sucked from the primary has to be replaced, which would mostly come from the atmosphere, given the cross-sectional area for the atmospheric opening is greater than the cross-sectional area of the transmission opening. Note: I didn't proofread - forgive me if a made an error. |
Originally Posted by BrandonSmith
(Post 18291696)
The crankcase is vented into the air cleaner. My understanding is that there isn't a pcv.
They are one way, which enforces the hypothesis of the possibility of there being crankcase vaccum acting on the crank seal. |
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