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Oil in the air boot? Why


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Gotta love the EPA... Should just vent to the ground...

You either run at high RPM, ride sand, or like to panic rev... I'm sure you don't overfill oil.

That's just excess blown thru the vent hose and is perfectly normal.

Thanks!  I do like to rev while I'm in the air, to try and stay on it!  Had a great lesson from my coach today!!  I run 1.5 liters, like the manual says…  

 

Thanks Steve!

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Why would there be oil (engine oil it looks like) in the air boot?  I was cleaning my air filter today, and noticed some puddled in the air boot area…?

Usually puddled oil is simply air filter oil. It's nearly impossible for engine oil to get into the airbox, but air filter oil gets puddled there all the time if you over-soak your filters like I do! LOL 🙂

Edited by tye1138
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Oil isn't going past the rings and into the cylinder's, then somehow past the valves, then through the air boot, through the throttle plate (impossible) and then into the airbox.

You're absolutely batshit crazy if you think that happens on a modern EFI 4 stroke.

 

Batshit must be the bomb, because you are absolutely wrong.

 

If you dont think oil is sprayed into the head and valves/cams, time to go back to shop class and see what keeps it from seizing up.... it's OIL.  IT IS VENTED or the engine will blow out the valve cover gasket, EPA does not allow oil to be shot out, so it is vented to the airboot...  Modern EFI 4 stroke 101 ..... learn it.

 

EDIT:  What do you think that hose is that comes from the valve cover of your 2015 450 and routes to the airboot?  A turbocharger?

Edited by steve841
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tye every engine makes positive pressure, no matter the injection system. That line coming from valve cover to intake is the vent. Usually there is a baffle, or maze of passages to keep the oil in but it doesnt always work.

Every model Honda 4 stroke has an internal vent, be it a 85 fourtrax or a 2015 crf450.

But ktms are hit and miss. 250/ 350 sx are external. But 450 is internal. No reason. easy to make right.

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If you dont think oil is sprayed into the head and valves/cams, time to go back to shop class and see what keeps it from seizing up.... it's OIL.  IT IS VENTED or the engine will blow out the valve cover gasket, EPA does not allow oil to be shot out, so it is vented to the airboot...  Modern EFI 4 stroke 101 ..... learn it.

Huh? I'm an engine builder, that's what I do in my spare time.

First off, a lot of dirt bikes vent to the ground. That's because oil doesn't come out that hole, it's simply an air vent. So how does only air pass through the system? Simple! There is a little box on the inside of the valve cover, that little box is full of baffles which allow air to pass through, but it's very tricky for the oil to navigate through. KTM has been using this design for a long time and sure, on some models they vent into the airbox, but not on all. If you were to pull the valve cover off and fill it with oil, you can see what I'm talking about.

Also, the head doesn't "retain" very much engine oil. In fact, a hot engine drains oil as quickly as it can get in. If it didn't, there would be a lack of oil in the crank cases very quickly. Yes, when an engine is tipped over, oil from the clutch area can slowly work its way up the timing chain path and into the head. However, unless it's upside down, there is no way the oil will go out the baffle. You may get a tiny bit of wetness out the vent hose when the engine first starts up as oil mixes with the air inside the crankcase, but it would get sucked back into the engine so quickly, there would be no way for a puddle to collect inside the airbox. Assuming your engine vents to the airbox, which quite a lot don't.

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Batshit must be the bomb, because you are absolutely wrong.

 

If you dont think oil is sprayed into the head and valves/cams, time to go back to shop class and see what keeps it from seizing up.... it's OIL.  IT IS VENTED or the engine will blow out the valve cover gasket, EPA does not allow oil to be shot out, so it is vented to the airboot...  Modern EFI 4 stroke 101 ..... learn it.

 

EDIT:  What do you think that hose is that comes from the valve cover of your 2015 450 and routes to the airboot?  A turbocharger?

 

I agree with Steve.  

 

My CRF 250 was vented to the air boot, along with a Y fitting for an additional clear tube with a plug in the end that ran down the frame.  That tube always filled with condensed clear oil, presumably oil vapor that condensed from the valve cover.

 

I bought the vent kit from applied racing to block off the air boot and put a short hose / filter on the crankcase vent, venting to atmosphere.  They still make them.

 

http://appliedrace.com/shop/index.php?main_page=product_info&cPath=42&products_id=1377

Edited by redrider144
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Tye, every 4 stroke engine has a crankcase vent, and most today are internal, be it lawnmower, supercharged mustang, ktm 450, diesel, etc. they do not all share the same venting methods, one might have an actual filter, or a checkvalve, or trap doors, or a sos pad, but all will pass oil thru to some degree. The more compression, the more likely it can happen.

At the same time if you took said vent off the intake to engine, where its originally having a vacum pulled, and just let it run open, any oil that might have been pulled thru while under vacum will most likely not be now. In a modern car with a pcv valve, they are more or less tryng to pull air thru the crankcase, but in the case of jeffs 450, just somewhere for it to go.

The internal vent can be bad for many reasons, but think about looping your bike out of something. Lots of times oil will definatly get pulled right thru.

Or when things start wearing, it would also push oil thru.

If it was open and you got upside down for long, oil just goes out, or when emgine gets tired you might see the vent or smell it and be alarmed of something.

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