Crankcase breather pros and cons?

Ducsauce · February 20, 2010, 09:50:25 AM

Okay so Ive been trolling through posts and many people seem to say to do the crankcase breather by pass for performance and cosmetic appearance. I can understand the cosmetic aspect but Im still confused about OVERALL performance gains, if any. Allow me to clear up any questions I can before I begin. I have a 2001 M750, bone stock. Carbuerated not fuel injected. It still has all the emissions cans and the little pod thingys on the side of the frame. I was just going over options for modifying and one of the easiest things seems to be the crank case breather.

1. My experience with motors is limited to my cars. Ive built show cars. I know some parts Ive put on the car were for "show only". The crankcase breather has always been one of those "show only" mods. Im no mechanical genius but I do know that the crankcase is vented into the intake in order cause a positive vacuum that increases oil flow into vital moving parts. If it wasnt designed to do that why would Ducati have it there?

2. How much of a real world gain can be actualized by this mod?

3. What damage can it cause over the long term use of such a thing? I know that in my cars it can lead to failure in the head and such not.

4. How, if at all, will this affect overall reliability of my machine?

I understand that the crankcase breather has the potential of venting "oily mist" back into the intake but after checking the area immediately around the port into the intake box that there is no buildup which is usually associated with any kind of worry that there will be damage to the motor. If anything I would assume that the oil thats that fine would help to aid in the lubrication in any parts in the top end more than cause any kind of harm.
Sorry if this seems simple to most but I dont want to take the chance of blowing my bike up through something that could have been left the heck alone! Thanks in advance all!!

ducpainter · February 20, 2010, 09:54:58 AM

There is some disagreement about the performance gains.

I don't believe there are any, and on 4V bikes there is actually a performance drop.

It's small, but proven.

Lots of bikes run with the filter with no long term ill effects.

Make it look like you want and be happy.

Ducsauce · February 20, 2010, 10:24:47 AM

Yes Im super new to all this, do I have 2V or 4V?

ducpainter · February 20, 2010, 10:27:06 AM

Quote from: Ducsauce on February 20, 2010, 10:24:47 AM
Yes Im super new to all this, do I have 2V or 4V?

Your 750 is a 2V air cooled.

All the 4V Ducs are water cooled

Howie · February 20, 2010, 05:09:09 PM

Ditto on what ducpainter said. Positive crankcase ventilation is required by law, it also prevents oil from being burped out, possibly on your rear tire. The reasons for eliminating the breather box are aesthetic or you need to for other modifications like pod filters. If you do choose to eliminate the breather box mount the filter high up to avoid oil burps.

He Man · February 20, 2010, 05:26:37 PM

If you could find a way to extend the neck of a pod filter by some length and plastic weld a nozzle onto it, you could directly connect the crankcase to the the intake.

Privateer · February 20, 2010, 09:47:20 PM

i'm wondering if there's a way to replace the ugly plastic tank with something a little more pleasing, maybe hang it off the frame with a clamp. I want to flip my rectifier over so it gets more cooling, but have to ditch the tank for that which I'd rather not do.

Langanobob · February 21, 2010, 02:47:01 AM

QuoteIm no mechanical genius but I do know that the crankcase is vented into the intake in order cause a positive vacuum that increases oil flow into vital moving parts.

I'm ready to be corrected on this, but I don't think the crankcase vacuum has much to do with increasing oil flow into vital engine parts. Plenty of oil flows into vital moving parts due to oil pump pressure and the crankcase pressure doesn't have much to do with it. But I could be misguided.

I think the positive crankcase ventilation does help to minimize the amount of wayward combustion chamber gases contaminating the oil. Years ago I hooked up a positive system on my old '66 Triumph which has a huge amount of crankcase gases compared to a Duc and it's worked fine with the additional benefit of stopping the legendary Britbike oil leaking. I was concerned it would foul plugs, but no.

I like Privateer's idea of a better looking tank. .

Howie · February 21, 2010, 03:05:38 AM

Quote from: Langanobob on February 21, 2010, 02:47:01 AM
I'm ready to be corrected on this, but I don't think the crankcase vacuum has much to do with increasing oil flow into vital engine parts. Plenty of oil flows into vital moving parts due to oil pump pressure and the crankcase pressure doesn't have much to do with it. But I could be misguided.

I think the positive crankcase ventilation does help to minimize the amount of wayward combustion chamber gases contaminating the oil. Years ago I hooked up a positive system on my old '66 Triumph which has a huge amount of crankcase gases compared to a Duc and it's worked fine with the additional benefit of stopping the legendary Britbike oil leaking. I was concerned it would foul plugs, but no.

I like Privateer's idea of a better looking tank. .

You are not wrong in either statement, though I'm not sure about the effect of oil cleanliness on a Duc, since there is always positive pressure in the crankcase, you are running a filter as good as an air intake filter and the valve is still there.

Privateer · February 21, 2010, 06:26:36 AM

Quote from: Langanobob on February 21, 2010, 02:47:01 AM
I like Privateer's idea of a better looking tank. .

after some searching around, something like this, but smaller. this one is 6" long.

fouramdesigns · February 21, 2010, 08:21:23 AM

I installed the TPO kit, I have some oil blowback, pools around the base gasket area. Spoke with TPO, he things the reed in the breather is bad. I just had the infamous base gasket leak repaired, so when I first saw this, I was worried.

Howie · February 21, 2010, 10:33:01 AM

Quote from: fouramdesigns on February 21, 2010, 08:21:23 AM
I installed the TPO kit, I have some oil blowback, pools around the base gasket area. Spoke with TPO, he things the reed in the breather is bad. I just had the infamous base gasket leak repaired, so when I first saw this, I was worried.

Could be, sometimes a reed will even break. If you still have the OEM valve, the valve itself could be leaking.

scott_araujo · February 22, 2010, 02:01:14 PM

I didn't think that was a tank between the crankcase valve and air cleaner, I think it's just a baffled chamber. The vapors always get sucked into the air cleaner but if you get an oil burp the liquid never gets past the baffles and drains back to the case.

Am I wrong?

Scott

ducpainter · February 22, 2010, 02:05:42 PM

Quote from: scott_araujo on February 22, 2010, 02:01:14 PM
I didn't think that was a tank between the crankcase valve and air cleaner, I think it's just a baffled chamber. The vapors always get sucked into the air cleaner but if you get an oil burp the liquid never gets past the baffles and drains back to the case.

Am I wrong?

Scott

You're correct.

stopintime · February 22, 2010, 02:06:46 PM

Quote from: howie on February 20, 2010, 05:09:09 PM
Ditto on what ducpainter said. Positive crankcase ventilation is required by law, it also prevents oil from being burped out, possibly on your rear tire. The reasons for eliminating the breather box are aesthetic or you need to for other modifications like pod filters. If you do choose to eliminate the breather box mount the filter high up to avoid oil burps.

If the filter is mounted directly on the valve, like most I've seen, where will a burp go? Into the filter, clogging it or through the filter making a mess? (tire?)

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Crankcase breather pros and cons?