KTM Breather Hose Mod....How much air is meant to come out?

pdee4t
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86
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7/15/2014
Location
AU
Edited Date/Time 11/9/2014 11:42am
Hi everyone.
I installed a one way check valve for the crankcase vent hose, as I had originally gotten water up through the vent hose. Did a bit of research online and worked out that quite a few KTM owners have installed one way check valves on their KTM's.
I bought a specially made check valve for it then vented the breather hose to the atmosphere, around the tank, then just underneath it to the other side of the bike....but when I put my finger just in front of the open end of the hose, I can barely feel any air escaping(it's very very faint).
When I put my finger over the hole and block up the hole for a second or 2, I can feel a bit more coming out and some very light vibration, but not very much, especially compared to my mates Yamaha YZ450.
it does increase with more rev's...but still not very much.

Im wondering if any other KTM RFS owners can verify how much air is meant to come out of the hose or if theirs is the same?
and also why the Yamaha's have a lot more air coming out, is it because the hose on the Yamaha's comes from the very top of the engine?
Apart from that, it runs and idles fine with it vented the way it is now. Not burning any oil or anything.

It's a 2004 EXC for those wondering.
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lumpy790
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9/18/2007
Location
York, SC, USA
11/7/2014 2:33pm
EXC as in 2 stroke?
11/7/2014 2:38pm
no, EXC-F. RFS is the "older" KTM 4-stroke motor.
Suns_PSD
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Austin, TX, USA
11/7/2014 7:43pm
When you have cylinder pressure leaking past your rings and valves they end up in your crankcase which is not where they are supposed to be.

Your buddies YZ just has a lot more engine wear than your engine. Yours sounds about right.
lumpy790
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York, SC, USA
11/8/2014 9:27am
Suns_PSD wrote:
When you have cylinder pressure leaking past your rings and valves they end up in your crankcase which is not where they are supposed to be...
When you have cylinder pressure leaking past your rings and valves they end up in your crankcase which is not where they are supposed to be.

Your buddies YZ just has a lot more engine wear than your engine. Yours sounds about right.
As a 4 stroke goes through its stroke it displaces at the same CC of air as the motor size in and out of the crank case. 250cc moves 250cc of air 450cc moves 450cc of air.

I am leery of installing a 1 way valve as the pressures are not good for the seals or gaskets. I have heard of people accidentally pinching the crank case hose and blowing out gaskets.

The Shop

pdee4t
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Location
AU
11/8/2014 11:02pm
my bike's motor doesn't have any crankcase oil seals in it.
lumpy790
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11707
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9/18/2007
Location
York, SC, USA
11/9/2014 11:09am Edited Date/Time 11/9/2014 11:10am
pdee4t wrote:
my bike's motor doesn't have any crankcase oil seals in it.
how does KTM seal the valve cover? Clutch covers? Ignition cover? Countershaft seal?
No-K
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Location
Sierraville, CA, USA
11/9/2014 11:42am

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