2014 Yz450 Crank Breather Mod

33 replies to this topic
  • drtrcr400

Posted November 01, 2013 - 06:16 PM


I've never liked having my crank breather hose open to the elements. When I purchased my new bike I tore it down to see what could be done. Coming from my 2012 I was hoping the new bike would have provisions for attaching the hose to the air boot. Turns out it only had the boss for the elbow. Ok, no problem I simply ordered the elbow and clamp from the previous gen bike. So the first picture here illustrates why this is an important mod in my book. This is the end of the hose that attaches to the valve cover. Note the particles of dirt after only 6 hours run time in non dusty conditions.

So off comes the air box.


The required parts.

A closer picture of the boss where the elbow will go.

The elbow installed after cutting out the center with a hobby knife. It's important here to cut from the out side part of the boot.

Now I noticed that the hose is slightly larger in diameter and doesn't clamp tightly enough to the elbow. I found a small section of shrink wrap and applied it to the elbow to make up the difference. I reinstalled the air box and pondered the best routing for the breather. Using the existing hose and shortening it only slightly I wrapped our around the front of the throttle body above the header. In this configuration I was able to avoid kinking the soft hose. I also noticed the extra protective layer on the hose is perfectly positioned above the header. Surprisingly this configuration also keeps the hose further from the header than stock. Here's the last pic I have.

I'll try it out tomorrow and let you all know how it works.

Edited by drtrcr400, November 01, 2013 - 07:11 PM.

  • BBrown626

Posted November 01, 2013 - 09:46 PM


Is there a drawback to hooking the vent to the air box that is at a lower pressure?

  • jc6711

Posted November 01, 2013 - 11:53 PM


If I am reading this correctly you are trying to vent crank case gases into the air intake like a car. If you are doing it this way you should incoporate a pcv valve. But a better way would be to re-route the house and put a filter on the end.

  • rhinoracin

Posted November 02, 2013 - 01:11 AM


If you route the hose anywhere you can see it above the engine, even if it has a filter, its possible for water to get in when you wash the bike

  • DC_Excitement

Posted November 02, 2013 - 04:08 AM


i did this mod on mu 2010 and it works great! could not feel any effects of performance and no could not see and oil getting into the intake after 10 hrs :thumbsup:

  • drtrcr400

Posted November 02, 2013 - 04:19 AM


I did the same mod with no ill effects on my '12 and ran it for 170 hours before I sold it. Before that it was a 2007 wr450. I put almost 400 hours on that bike. Now my cousin owns it, and it's still going strong. Seriously folks this works.

  • krony506

Posted November 02, 2013 - 04:37 AM


Nice job and thanks for sharing!  

  • SAthump

Posted November 02, 2013 - 09:08 PM


So in doing this you're not having any oil pool in the low point of the vent hose, or water after washing your bike?

  • drtrcr400

Posted November 02, 2013 - 09:23 PM


So in doing this you're not having any oil pool in the low point of the vent hose, or water after washing your bike?

Never had a problem before.  I, and others here have been doing this for years now on various bikes.  Just put in almost 50 miles of mixed riding today.  Some wide open 5th gear sections but mostly first and second gear tight technical stuff.  I let a couple different KTM nuts ride my bike as I followed on theirs, not a hint of oil smoke or smell.  As far as washing goes, you would have to almost fill the airboot with water in order for any to get into the hose.   Your much more likely to have a problem with the stock setup if you stall out in a deep water crossing.

  • Garett0439

Posted November 03, 2013 - 07:06 AM


With the stock breather hose me and my brother both got loads of water in our oil when we stalled in deep water crossings. My brother got so much water in his oil that it turned into what looked like expanding foam and began blasting out of the breather hose. I had to ride out of the middle of Fordyce creek trail and bring him back oil. We drained his old oil into a pile. Not a puddle, it made a PILE of oil.

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  • ca412686

Posted February 21, 2014 - 08:35 PM


How has this mod been working for you? Any ill effects?

  • DC_Excitement

Posted February 22, 2014 - 06:52 AM


still working just fine for me, cant find anything negative about it

  • drtrcr400

Posted February 22, 2014 - 08:20 AM


How has this mod been working for you? Any ill effects?

I have nearly 40 hours on the bike now and no problems.

  • ca412686

Posted February 22, 2014 - 08:28 AM


Awesome. I had the custom made oil separator like the graves for my supermoto, but this bike is for the trails. Gonna have to do this as well. Lots of water crossing and it's always a race! (All ex-racers) and someone always ends up on their butt!

  • ca412686

Posted April 23, 2014 - 03:47 PM


Just finished this mod. The pics helped a lot. Thanks!

  • Zien19

Posted April 25, 2014 - 07:50 AM


I did a version of this mod as well. But i also inserted a Tee fitting in and left the lower vent tube in place. Thanks for the info!!

  • drtrcr400

Posted April 25, 2014 - 08:17 AM


I did a version of this mod as well. But i also inserted a Tee fitting in and left the lower vent tube in place. Thanks for the info!!

I hope you capped off any part that may be open, if not you've introduced a path for unfiltered air to get into your intake.

  • Hoosier-Daddy

Posted April 26, 2014 - 08:17 PM


The T seems to be the way to go. This topic is covered in 'Common threads' under breather tube re-route.

Edited by Hoosier-Daddy, April 26, 2014 - 08:22 PM.

  • Zien19

Posted April 26, 2014 - 08:39 PM


Changed it around after thinking about it. Thank You TTers.

Edited by Zien19, April 27, 2014 - 07:53 PM.

  • grayracer513

Posted April 27, 2014 - 03:05 PM


NEVER allow unfiltered air into the air box. 

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