Breather Hose?

I have a 2013 YZ 450.  I am curious about the breather hose that comes off the valve cover and runs all the way to the bottom of the engine.  I ride single track and at the dunes.  Recently when I took the valve cover off, I notice sand had been coming up the breather hose.  My question is:  Does that hose need to be that long? I would like to cut it off shorter and put an UNI filter on the end of it.  Is there any reason I should not do this?  


Thank you for your input

There are a few different options from adding a filter to re routing it to your air box. Search "breather hose mod" you will find everything you want to know.

But by doing either one,  it doesn't cause damage right?

But by doing either one, it doesn't cause damage right?

damage no. If you choose to run it into your airbox, you may have to cut or drill a hole, but neither that nor the filter option will damage your motor. I am however skeptical of the air box route as it adds hot air to the intake system. This may or may alter the performance considering that our fi bikes have an air temp sensor. But again it wont damage anything and may be worth it compared to damaging your motor from sucking in crap. I recently pulled my cover off and found a bunch of fir neddles had been sucked in. Im considering my options also. I will probably go the filter route

Yeah I am just going to put a filter on it.  Thank you for you time and input

Yeah I am just going to put a filter on it. Thank you for you time and input

although i am considering a filter, i have always had hondas and yamahas. Both have this issue and i have never before changed anything with the vent hose. No bike i have ever had wore out what i would call prematurely. That said i think doing anything with the vent is more of a personal preference for peace of mind more than anything.

I just have concerns, because I only had about 50 hours on my bike and I broke a bucket, which caused the engine to seize.  It could have just been a faulty part, but there was some sand in there, so I don't know if that was the cause.

Did you replace the valves? If not you should. Good chance its bent.

I replaced all the valves. Springs. Piston. Rod. Crank. Literally everything just to be safe!

Sweet. Ride on

I had to repalce the head on my YZ because of sand coming up the breather hose.

When adding a filter to the end and nothing else, be careful to avoid restricting flow.  If crankcase pressure is allowed to rise too far, it can push out the half moon sections of the cam box gasket. 


The best procedure is to place a T about 6" down from the cam cover and run a second branch hose back to the air box.  This reduces the ability of the piston upstroke to raise anything up the tube by more than 100% while allowing expelled oil to drain away normally.  You can add a filter to either or both ends, or not at all.

Grey, is there a specific topic that might have picture of this?

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