Tuesday, January 18, 2011

KLR Crankcase Breather Hose Mod

KLR650E Crankcase Breather
I’m not quite sure what the Kawasaki engineers had in mind when they designed the late-model KLR 650 dual-sport motorcycle, but I can only guess that endless wheelies were not part of the equation. Amongst other well documented design flaws, er, ahem, features, there is this crankcase breather hose issue. Engine oil is allowed to drain from the crankcase into the airbox while these bikes are tipped in wheel-up position. To make matters even worse, the airbox actually draws oil into it as it is under a low pressure condition while the engine is running.

The New Crankcase Breather Hose
Fortunately, Mr. Kawasaki’s team had the foresight to put a fancy little drain hose and plug to easily get the oil out of the impossible to access clean carburetor side of the airbox. To prevent this oil suckage from happening in the future, the whole situation is easily remedied with a couple bucks spent at the hardware store and a couple of hours in the garage.

Breathe That Fresh Air
So, I got a few hardware store bits and removed the KLR’s stock crankcase breather hose. Out came the knife. Cut. I spliced in three feet of clear vinyl hose (1” outside diameter) and routed it up under the gas tank to arrive at an upper left fairing venting position. I threw on a 90 degree elbow. That way, if any oil did manage to make it all the way up there, the oil would be free to drain in an environmentally unconscious way to the ground. Part of a Briggs and Stratton lawnmower air filter prevents debris from entering the engine via the new vent. A penny blocks the airbox hole left over from the stock crankcase breather hose.

Plug That Airbox With a Penny
How does it work? Wonderfully. Oil no longer gets sucked into the airbox during whoolie sessions.


  1. My question is, will the vinyl hose handle the temps of being right next to the engine?

  2. @H3llpl3ss_KLR The vinyl hose is amazing at taking abuse. It's been filled many hundreds of times with hot engine oil and is performing as expected. This was a concern at installation, and another material would certainly be more suitable, but it does work well.