Author Topic: Crankcase/head ventilation  (Read 740 times)


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Crankcase/head ventilation
« on: January 08, 2017, 10:37:56 AM »
GY6 engines have a vent tube from the head cover that connects to the airbox.  The tube runs into a separator that condenses the oil mist into a foam filter and down into a "puke tube".  The air is then directed back into the intake downstream from the air filter. 

The separator often seeps grungy oil into the airfilter and drips down on the engine and CVT cover.  I already replaced the separator gasket once and it's still messy.  I also don't like the idea of contaminated air being redirected through the carb. 

Hooked the head vent hose up to the bottom of a plastic bottle and ran a vent hose out of the top with foam loosely packed inside.
Blocked off the passage into the intake.  While I had the airbox off I thoroughly cleaned up all of the grungy seepage which was surprisingly in a lot of places.

The plastic bottle is uphill so any oil collected in the foam will drain back down into the engine.  Later I plan to put a small metal bottle or can to replace the plastic bottle.  You must make sure air pressure can easily vent through the top outlet hose.

Yes, the collected oil is somewhat contaminated and drains back into the engine.  But it is a small amount and I religiously change the oil every 500 miles anyway.  It's nice to not have to drain the puke tube and not have oil seeping out of the separator making a mess.  You could mount the bottle downhill and drain the oil out manually, instead of letting it flow back into the head. 

If you keep the engine oil level halfway up the dipstick instead of completely topped off, this greatly reduces the amount of oil pushed out the vent hose.  I'll post a photo later today.
« Last Edit: January 08, 2017, 04:06:42 PM by scooterist »
2014 Lance PCH 150

Prima medium windshield, 9.25 gram sliders, variator boss shaved 1.5mm, #115 main jet, air cutoff valve disabled, airbox/carb mods, desmogged, digital tach, body integrated front turn signals, ventilated CVT cover, passenger footpegs, LED taillight, seat bucket hump removed.