If the kleen air system is a vacuum system and draws clean air from the air box as the DIY & service manual state....where does the engine vent excess pressure? My previous two bikes dumped back into the air box injecting goo which is then caught by the air filter before re-entry. Does my ninja have something similar?

first off... the kleen system and engine pressure have no relation here.

from what I understand of the kleen system, it draws clean air from the airbox via that vacuum operated air switch located above the engine. The air is then allowed to pass from the airbox to the exhaust side of the head and mixes with the exiting exhaust from the engine under certain loads, dictated by that vacuum switch, to lean/clean the exhaust gases.

crankcase pressure is internal to the engine, completely separate from the exhaust side that the kleen system supplies clean air to.

there is a crankcase vent located in the top middle of the crankcase connected to the bottom of the airbox via a (3/4"?) hose which collects the air/oil vapors from the engine and routes it to the airbox for filtering and reuse.

I understand the kleen air system.

Thats what I am looking for. So there is a hose from the crank to the air box. Would you be able to tell me the ID of that 3/4 hose....1/2" maybe?

dunno for sure... it's right there on your bike. :)

I understand the kleen air system.

Thats what I am looking for. So there is a hose from the crank to the air box. Would you be able to tell me the ID of that 3/4 hose....1/2" maybe?

Yup, crankcase to air box. It's not filtered before being sucked up by the carbs.

Yup, crankcase to air box. It's not filtered before being sucked up by the carbs.

Really? I am suprised about that if you saw the crap that comes out of it. It might be worth while re routing.

Really? I am suprised about that if you saw the crap that comes out of it. It might be worth while re routing.

crap... what crap?? it would be oil, air or water vapor.

re route to where? if you go to an unfiltered side of the airbox, you stand a chance of ingesting uncleaned air when it vents air into the engine instead of out. better to stick a filter on the end of the hose if you're concerned about it. I removed the airbox on my bike and presently have a filter on the end of that hose.

Plus it kinda keeps a vacuume on the crankcase. Suppose to help it rev better, so all the drag racers say.

I had rerouted to dump out on the ground and plugged the hole in my air box. I was told it would clean up combustion.