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-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (http://xlforum.net/forums/showthread.php?t=2073932)

Hippysmack 28th July 2019 02:52

Quote:

Originally Posted by dieselvette (Post 5765731)
It's not that big of job, but you are right if you're paying someone to maintain the bike then the krankvent is a good value (assuming it will last for 50,000 miles, because it's not cheap).

But, it wouldn't bother me a bit to swap umbrellas once a year on some wintery day. STILL not trying to defend the stock valves, I'm just saying it's not a deciding factor for me.

I agree.
I take things apart every winter and sometimes in between.
So I guess I don't see the big deal with pulling the rocker covers.
It's just a few bolts.

60Gunner 28th July 2019 03:03

I'm sick of pulling the rockers thanks to oil leaks caused by the failed breathers before I figured out the problem.
Maintaining little or no pressure will make leaks non existent.

dieselvette 28th July 2019 03:05

Quote:

Originally Posted by Hippysmack (Post 5765708)
I guess I didn't think about when they get stiffer, the don't open as well.
Even if they do seal on backflow, they could still raise pressure on downstroke.

Could be, but no one is saying that tiny difference matters. We don't know that these valve are bad. The only way to know that is to put them on a bike that has stock umbrellas and no breather problems to begin with.

Hippysmack 28th July 2019 03:27

Quote:

Originally Posted by dieselvette (Post 5765737)
Could be, but no one is saying that tiny difference matters. We don't know that these valve are bad. The only way to know that is to put them on a bike that has stock umbrellas and no breather problems to begin with.

True.
So many people seem to hate them. I find that ironic based on Aaron's testing.
That's what makes me wonder exactly where the problem lies.
You can't make a case without testing.

I'm not advocating either way. I would like to see more testing however.
Decommissioning them like tomcat mentioned is a personal preference.
Nothing wrong with that.
I just can't see telling everybody their OEM breathers are junk without proof.
That ain't right.

Quote:

Originally Posted by Tomcatt (Post 5765735)
On mine it's a BIG PITA because of the BS plastic housing above the heads all the wiring runs in. At some point I'll pull the heads to get valves and porting and I'll deal with the wiring mess then. If it wasn't for that it wouldn't be too bad pulling rocker boxes, heads etc.

I didn't realize it was such a chore on rubbermounts.
It's intentional bonding to me.
Makes us both feel good. :)

dieselvette 28th July 2019 04:01

1 Attachment(s)
Quote:

Originally Posted by Hippysmack (Post 5765708)
Did you find a hole, even tiny, between the orange rubber and the opening for the mesh?
I can't see one in your pic either.

There is a hole, and it will pass air and bypassing the umbrellas. It's about 0.060". See picture. Both valves have it.

Could be there to prevent building up pressure/vacuum while parked and not running - but it wouldn't have to be that big then, they could have made it smaller and only on one. Makes me wonder if it's not very picky how well the valves seal, as long as they "sort of" work.

For the record, far as I can tell I had no breather problems. I did have above-average blowby and bad valve guides judging by what I saw at teardown. With the stock vent-into-carb setup, I never had any oil buildup or evidence of oil in the intake or carb. All clean as a whistle. 60,000 miles never had the motor apart, and zero oil leaks. (so, no oil puking problems).

It's conceivable that my breathers were too restrictive to vent off the amount of blowby. And that could explain why the Bikers Choice oil cap would leak to bleed off pressure. (Tank vent line is in perfect order, no restrictions).

Edit: Not the breathers restrictive, the restriction would be the hole in the mount bolt. So had I drilled those out, maybe would have relieved the CC pressure (if in fact there was any).

I did have a wetsumping problem, which got progressively worse over the last 10,000 miles. I'm really confused how blowby + crankcase pressure would cause a wetsumping problem, if that's in fact the case.

60Gunner 28th July 2019 04:18

I'm not saying the stock breathers are junk either or everyone should run out and replace them. I do think the krankvent is a better alternative especially if your stock ones aren't up to par anymore.
For me it was a no brainer as I've never cared for the breather hoses hanging. So when I realized my stock breathers were bad, it's all I needed to look into better alternatives. I'm glad I did and I'm more than happy with the outcome.
I think people should be aware there's another alternative that does a little better job at the very least, is easier to maintain, and lasts longer.

Yeah, I've cleaned up the stock wiring mess. Still sick of pulling the rockers.

Hippysmack 28th July 2019 04:33

Quote:

Originally Posted by dieselvette (Post 5765745)
There is a hole, and it will pass air and bypassing the umbrellas. It's about 0.060". See picture. Both valves have it.

Thank you veeerrry much.
I wondered how the MoCo would handle oil that by default would sit in that 'shelf' as I call it between the inlet and outlet of the unit.
Think about it.
The 91-03 umbrellas sit with the tiny hole down into a recess 'to collect oil and drain it that gets passed the umbrella.
I wondered if they expected suspension to move the oil out that sits in that recess in the rubbermount since I couldn't confirm the hole there.
But if oil does collect there and rise into the air path, it stops up the breather.
edit: (wouldn't this resemble venting the oil tank with oil level so close to the vent?)
Oil drain.....

The more ring blowby you have, the more positive pressure you have which aides in pushing the oil to the scavenge port.
But also the more oil that is picked up and splashed into the breather valves.
So more blowby equals more splash oil picked up into the air/mist.
The pressurized air/mist is directed toward the breather vents since during (during downstroke) pressure builds but the vent outlet is at atmosphere.

Going back to DK Custom's data chart, you can see that at redline or even in that realm of high RPM, blowby is much greater than at idle.
This is why we have more oil puking at high RPM.

Hippysmack 28th July 2019 04:43

Quote:

Originally Posted by 60Gunner (Post 5765748)
I'm not saying the stock breathers are junk either or everyone should run out and replace them. I do think the krankvent is a better alternative especially if your stock ones aren't up to par anymore.
For me it was a no brainer as I've never cared for the breather hoses hanging. So when I realized my stock breathers were bad, it's all I needed to look into better alternatives. I'm glad I did and I'm more than happy with the outcome.
I think people should be aware there's another alternative that does a little better job at the very least, is easier to maintain, and lasts longer.

Yeah, I've cleaned up the stock wiring mess. Still sick of pulling the rockers.

Nobody's accusing you of anything Gunner.
I'm going over hundreds of posts in my head from previous.
I can't even remember how many times I've read that.
I'd hope that someone searching the forum later would come across this thread,
And at least read of these posts that suggest there is an alternative, and a good one no doubt.
But they don't have to go out and spring for it unless they chose to.
Reading other threads, any alternative to OEM seems to be prevalent.
So I'm not picking on ya.
Just trying to help the next guy, who hopefully can make their own good descision of what to do.

dieselvette 28th July 2019 05:14

1 Attachment(s)
Quote:

Originally Posted by Hippysmack (Post 5765751)
I wondered how the MoCo would handle oil that by default would sit in that 'shelf' as I call it between the inlet and outlet of the unit.

Good catch - it's definitely an oil drain. Makes sense as it's on the down-hill side of the housing. Are you also aware there's a wall inside to stop the oil. See picture. Above this weirs, there is probably a 1/16" gap. The oil would have to fill almost the whole plastic housing (this being after having gone through foam + umbrella) before it would come out the vent.

So it makes sense then, why I have no trace of oil in my intake.


Quote:

Originally Posted by Hippysmack (Post 5765751)
But also the more oil that is picked up and splashed into the breather valves.

How is it picked up, moreso than under regular conditions? Due to denser air, more turbulence?

60Gunner 28th July 2019 05:16

Quote:

Originally Posted by Hippysmack (Post 5765755)
Nobody's accusing you of anything Gunner.
I'm going over hundreds of posts in my head from previous.
I can't even remember how many times I've read that.
I'd hope that someone searching the forum later would come across this thread,
And at least read of these posts that suggest there is an alternative, and a good one no doubt.
But they don't have to go out and spring for it unless they chose to.
Reading other threads, any alternative to OEM seems to be prevalent.
So I'm not picking on ya.
Just trying to help the next guy, who hopefully can make their own good descision of what to do.

I'm not saying you were. Just clarifying my position because I am, and have been, highly advocating both the krankvent and relocation to the cam chest as worthwhile upgrades.


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