Sealing (isolating) primary again.

[ricochet]

I've read all I could from the search feature but a lot of it relates to Shovel engine.  So on an Ironhead Sportster when you isolate the primary from the engine this includes the transmission as well, right?  I can see where the breather valve needs to be plugged between the left crankcase and the primary.  And I also see there is a "oiler" cap type device that oils the transmission counter shaft and gears.  When done with this isolation does the tranny and primary share the same oil.  I can figure what lines need to be capped and the necessity for venting both the engine and the primary seperately but was wondering about the tranny.  In order to lube the tranny sufficiently does that pose a problem with the level in the primary?

ricochet

[eglideic]

 There is no need to isolate anything.
Harley  has it right from the get-go.
Leave it alone.

[Lew]

Yep, leave it alone.  The reason for isolating the primary oiling on shovels is because the oil is shared with the engine....not good.  Sportys share there primary oil with the transmission.  No worries.

Lew 

[ricochet]

OK,  so what of this valve or vent between the the crankcase and the primary?  Does that not let engine oil mix with the primary?  This is on a 73 ironhead that according to the manual is a wet primary for that year.

Thanks guys,

ricochet

[nibroc]

when running a dry primary-that vent valve is blocked

[Maddog]

the funny thing is that for a 73 the engine an tranny oil are the same   as in 50wt in the engine an 50wt in the tranny etc etc    The primary oil an tranny oil are in the same compartment,

[wreck74]

I think the valve between the engine and primary is the vent for the primary and transmission. It vents into the engine instead of venting into the atmosphere. I could be wrong.

[saltcaveminer]

ok there is no vent between the crankcase and.the primary. that thing is called an oil transfer valve.it will only transfer oil to the primary if the crankcase pressure builds up.they are completely separate compartments.the transfer valve can be sealed but if the breather valve should fail then you might blow the shaft seal.that cap on the countershaft takes splashed oil and lubes the countershaft bearing (the hole facing up).the primary cover cap is vented.Salty

[Blackcherry Low]

the funny thing is that for a 73 the engine an tranny oil are the same   as in 50wt in the engine an 50wt in the tranny etc etc    The primary oil an tranny oil are in the same compartment,

Not all that funny really.  Not uncommon for older bikes to use the same grade of oil for eng and trans, but it is not shared between the eng and trans on the 70s Ironheads. 

I would imagine that one of the reasons why they use the same type oil is because of the vent between the crankcase and primary case.  I'm sure you will get some mist from the crankcase into the primary and of course if your check valve in the oil pump leaks, the oil that leaks into the crankcase will rise and eventually overflow into the primary case.

I don't know the actual reason for the vent but I can only imagine they needed the extra space of the primary case to properly vent the crankcase.

I wouldn't plug it off, I don't know what the pluggers hope to accomplish by doing so.  But I don't have all the experience that some of you guys do. 

If you are constantly getting excess oil in the primary, the better option would be to fix the root of the problem rather than put a bandaid on it.  Otherwise you'll be constantly adding oil to your tank and cleaning up a big mess from the breather on your garage floor and performing undue maintenance on the primary case.

[ricochet]

This is quite interesting.  Here I thought that isolating the two cavities was a given on all these ironheads since now there are such better gear oils available for the tranny.  And the 73 is a wet primary anyhow.

ricochet

[Blackcherry Low]

O.K., I was way off on my theory , well, not that far off I guess.

Just did some more research and the oil transfer valve is supposed to be a one way valve from the primary to the crankcase.  I just watched a you tube vid from a guy that has a fitting tapped into the hole and he hooked up a hose to it and demonstrated with the engine running how the crankcase will draw air through the valve to control vacuum as the pistons move upward.  Cool video, he sucked up a bunch of oil into a container in short order.

But the way it sounds to me is that when the engine is not running the valve is probably open or at least not seated and that's how engine oil that has leaked past the oil pump check valve floods the crankcase and eventually overflows into the primary.

"A bit nutty eh"