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Rerouting crankcase vent hose? KTM/Husky 450 -17

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Hi

 

I have seen some proos rerouting the crankcase vent hose from the airboot to underneth the bike.

They say the bike will suck hot/contaminated air and therefore loose power.

 

What do you guys think? Is it true?

 

I guess it is best to use a one way valve on the hose if you rerout it so it wont suck water if you crash in a puddle? Or is it unnecesserely?

 

 

 

 

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On my XRs I close off the under bike vent and install a K&N filter into the top of the hose. Just check the bottom of the hose for condensation accumulation at regular intervals.

 

I do this because air flows in and out of the hose on each piston cycle and I don't want to risk water or dirt being ingested into the engine.

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For on road riding I disconnect the hose from the air box and plug the cavity with a tapered silocone plug. Then I attach an 8mm straight brass barb and a long hose which I route aroung the wiring under the seat the face it down next to shock absorber spring. Less oiily gases to your intake which is a good thing. Also in the event of oil blowback, the oil will flow outside, bot into your air box.

The drawback is that this is not a reliable solution for off road riding, water could easily find its way into the hose then your crankcase, if the bike falls into a deep puddle or a river.

This is a vent hose, therefore do NOT use one way valve, only a fine mesh screen filter.

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For on road riding I disconnect the hose from the air box and plug the cavity with a tapered silocone plug. Then I attach an 8mm straight brass barb and a long hose which I route aroung the wiring under the seat the face it down next to shock absorber spring. Less oiily gases to your intake which is a good thing. Also in the event of oil blowback, the oil will flow outside, bot into your air box.

The drawback is that this is not a reliable solution for off road riding, water could easily find its way into the hose then your crankcase, if the bike falls into a deep puddle or a river.

This is a vent hose, therefore do NOT use one way valve, only a fine mesh screen filter.

 

Hi

 

what purpose has the straight brass barb? And where on the hose do you put it?

 

Does a fine mesh screen filter let the air out from one side but keep the water out from the other?

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The base connects 2 hoses together, so you can route that extension anywhere you want to make it safe.

No, the mesh won't keep water out, only debris. Unfortunately, any kind of vent hose we talk about will need 2 way flow, on your crankcase, carb or tank, everywhere. On dirt bikes, there is no point fitting one way valves, it is actually dangerous, especially on a crank breather hose.

To keep the water out simply leave it stock, connected to the air box. This is the only reliable way for off road riding.

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This is what I did with mine after 2 grand worth of motor repairs from sucking mud into my motor.

1470318541154.jpg

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Truth is , atleast on my 500 ,there is a lot of pressure coming out of that hose , not only at idle but even greater at rpm,  any kind of blocking or restriction of that hose can cause issues.

 

Im vented to air and uder the bike, have been for nearing 20,000 miles,  same piston , same original factory valve settings , they've never needed adjustment yet.

 

 

 

My testing there is a very tiny inhale on intial start up , so I guess if the motor was under water, and having trouble starting, you might be able to draw water I suppose, but once the motor actually starts, it blows outward strongly.

 

 

 

In severe cold weather having the vent hose connected to the airbox, does offer warm air until the motor is fully warm, but in extremely hot weather, the hot contaminated recirculative air can have the opposite effect.

Edited by Spud786

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On 8/4/2016 at 5:14 PM, highmarker said:

Leave it stock, it's not contaminating the intake charge unless your engine has issues.

It's going to be hot air blowing into the air box, however--especially during the summer, which can rob the engine of hp, right?  I'm resurrecting this thread because I'm in the midst of a desmog/uncork/vortex project on my 2018 KTM 350 EXC-F and trying to figure out whether to reroute.  Not a lot of recent posts on this subject that I can find.

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On 11/6/2019 at 12:15 PM, mhk said:

It's going to be hot air blowing into the air box, however--especially during the summer, which can rob the engine of hp, right?  I'm resurrecting this thread because I'm in the midst of a desmog/uncork/vortex project on my 2018 KTM 350 EXC-F and trying to figure out whether to reroute.  Not a lot of recent posts on this subject that I can find.

Mine has been re-routed into the frame. I destroyed my engine from a water hole because of it.

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How much power are you really losing here? Have you found an actual figure?

I say leave it be.

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1 hour ago, HansLanda said:

How much power are you really losing here? Have you found an actual figure?

I say leave it be.

Nope--just trying to read up on it, and had the exhaust/rear spring off while desmogging, so wanted to take care of it at the same time, if it was a go.

I left it as-is.  

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