Here is some information on a variation of the crankcase vent mod from KTM land. The guy that did this video is a rider and has his own shop and is highly respected for his work. He demonstrates a one-way valve and the effect it has on your engine. This would be applicable to the KLX250S as well. Obviously, the larger the displacement, the more effect one of these has. Is it going to be huge - no, but every little bit helps and several smaller mods can add up to be noticeable.

As recommended to me by Jerry Leighton, I re-routed my crankcase breather up to the airbox and put a filter on it for better breathability. But it was Marty who did the PCV mod which used a 1-way valve similar to the mod below, the main difference being that the valve below is designed specifically for this application.

Anyway, I thought this might be useful information for anyone here who wanted to do this and/or know specifically the effects and benefits.

http://www.youtube.com/watch?v=i-x5pO9Vi70

 

Now that sums up of everything ,, Thanks For Sharing NB

 

Good info. Thanks.

 

Very cool. Where do I get the valve?

 

any auto parts house or possibly hardware store would have a one way check valve. I would think, but dont qoute me on that lol

 

Here is his on-line store:

http://www.ThumperStore.com/

And here is the valve:

http://www.thumperstore.com/Case_Ven..._case_vent.htm

 

Cool thanks.

 

Brian,

Help me out here. The crankcase breather on a KLX looks like a 1/2 or 5/8 auto style hose. I've seen the thread from Dirtsurfer on the one day mods where you re-route the breather to the top of the airbox, just under the seat and then connect a filter. Never like to ***-you-me anything, but it seems that an adapter to get down to the breather valve is necessary. True story?

Concept makes a lot of sense, as anything that will limit foreign matter into crankcase oil is a good thing.

 

The stock routing for the KLX is good in that it filters any dirt because it is behind the air filter already. The value in rerouting underneath the seat is that it allows you to open up the passage way making it a little freer flowing without having to drill the airbox and possibly getting plastic shavings in the carburetor. With the filter on the end after rerouting, that should take care of any dirt. The 2nd benefit is that if you tip over with the bike leaning downhill oil from the crankcase is not going to fill the airbox / carburetor and leaving you low on oil, but worse, possibly even enter the cylinder directly and result in a hydrolock - yes it has happened. If you hit the e-start in that condition you could possibly bend the rod. The filter at the end of the vent tube should prevent oil from coming out as well, at least it appears that it would, and if it does it would just harmlessly go into the airbox harmlessly onto the filter not right into the intake passage like the stock routing.

The advantage of the 1-way valve is that there is an overall negative pressure in the crankcase resulting in a slight additional performance gain, i.e., less air to move back and forth from atmosphere. Also, no oil to spill as in the 2nd benefit mentioned above. And it ensures no water in the crankcase too.

But don't expect a big seat of the pants difference. I would put this in the category of if you like to know you have done everything you can for your bike, this would be one. Also, it's cheap, esp. if you adapt an auto PCV valve instead of the $70 purpose built valve above. But the idea is the same.

 

All good points. there is room to slip a pcv into the stock hose/airbox setup.