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06' KLX 300 Crank Case Breather Mod

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Does anyone have pictures or know where to find information on how to do the Crank Case Breather Mod? Pictures would be helpful since I'm not familiar with what everything looks like. I don't usually work on my bike but I have heard this mod makes a difference. My bike has a aftermarket exhaust and jet kit. Any help would be much appreciated.:thumbsup:

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I did the mod too, and the PlanetKLX instructions are clear. I got the hose at the auto part store and the recommended filter at the motorcycle shop. I used a short half-inch bolt to block the open end of the stock hose after I disconnected it from the crank case (have enough hose clamps though because I couldn't use the original one to secure the bolt on the stock hose like the site suggests).

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Not to hijack,but..........what does this mod really do???? My brothers bike has the mod and mine does'nt. I can't tell the difference. Maybe a stupid question that has already been answered, but I have'nt seen it:confused:

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I had a mechanic suggest that it might keep the jets cleaner since oil could get sucked into the carb through the crankcase hose.

He also said they do this mod to all of their race bikes.

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The piston going up and down displaces volume in the crankcase. This mod allows freeer (freer? free-er? more free? easier!) flow of that air.

I think it is preferable to simply remove the restrictor and leave it connected to the airbox where there is a slight vacuum to evacuate the blowby from the case. This minimizes contamination of the oil with combustion products.

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Except for two strokes which need crankcase pressure to feed the cylinder, piston engines generally use a breather to relieve the build up of crankcase pressure and vent the oil vapours. As the piston comes down and the engine heats up, it pressurizes the crankcase. The air and oil molecules also expand to cause more pressure. If too much pressure builds, you can get leaks or even blow up the case.

Eliminating restriction is desirable because it allows the piston to travel downwards without the resistance caused by positive pressure in the crankcase. Opening up the restriction in the stock KLX breather hose provides lets the engine rev more freely. Another benefit is that more horsepower reaches the rear wheel because the piston isn't pushing against positive crankcase air pressure (much like a bicycle tire pump).

It's a pretty minimal gain as far as performance enhancements go, but because it's cheap and easy, it's a popular mod.

Adding the filter on the end prevents oil vapour from fouling the air filter and possibly clogging the jets.

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ive been wondering exactly what this mod does and doesnt do and even if its worth doing .ive heard that it has very little effect on hp gain if any. but it also sounds like it might be worth doing anyway as its cheap and easy.

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See the Colorado Kings response above, its basically cheap insurance.

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i cannot find anything on Planet KLX. is it still a viable site or am i doing something wrong????

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Has anyone on here done this mod and really noticed any improvement in performance? I haven't done this mod myself (yet?). From what I have heard and read there is no noticeable increase in power and you chance mucking up your air filter in a tip over. I'd be interested in knowing if anyone who has actually done this mod has noticed any improvement.

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I think modifying or replacing the stock breather plug is easier than buying an external filter and running a new hose back into the air box. Especially if you keep the air box lid and just remove the snorkel. That way you get effective suction from the intake through the lower air box to help remove air in the crankcase. True the air it doesn't go through a filter, but I really don't think that is a big concern. My custom plug has a 5/16 ID and the same OD; I made it slightly longer than the stock version and works well.

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