guess Im gettin old - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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\ From the radiator, through the case and out
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post #1 of 11 (permalink) Old 08-14-2013, 12:45 PM Thread Starter
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guess Im gettin old

where exactly is the crankcase breather on this engine, dont see one anywhere, how does it vent off pressre.
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post #2 of 11 (permalink) Old 08-14-2013, 01:01 PM
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Three crank case breather it's tied into the air ducts via the surge tank

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post #3 of 11 (permalink) Old 08-14-2013, 01:09 PM
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Quote:
Originally Posted by artstoy View Post
where exactly is the crankcase breather on this engine, dont see one anywhere, how does it vent off pressre.
On the front of the engine, coming out of the block almost right behind the fan, the hose goes into the front end of the surge tank. There's a smaller drain hose off the surge tank about 3-4" from the crank vent. Look right behind the fan motor and you should see it. Vacuum in the surge tank pulls some air out of the crankcase, or road draft in the case of an earshave.

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post #4 of 11 (permalink) Old 08-14-2013, 01:20 PM Thread Starter
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so basically there is no crankcase vent, it relies on the airfilters and the breather tube from the carburators. So what exactly stops this engine from building up crankcase pressure, I dont see how incoming air through the valves has any effect on the lower crankcase, removed the surge tank, the hose that was on the bottom nipple was already gone, and as i understand it the emission was to simply introduce cooler air from the smaller tube in the surge tank into the exhaust area, which again doesnt have any effect on crancase pressure, typically you will see a vent on a valve cover or back upper portion of crankcase itself. so curious to how it vents. so a little confused on logical thinking here.
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post #5 of 11 (permalink) Old 08-14-2013, 01:34 PM
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I hope those pictures show where the crank case vent tube is.
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post #6 of 11 (permalink) Old 08-14-2013, 01:47 PM
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There's vacuum in the surge tank due to the carbs pulling air through the tank, like the PCV system on a car engine, which pulls crankcase air out via a valve cover with vacuum from the intake.

With an earshave, it's just wind drafting over the filter, like a road draft tube on a 1950s-early 60s car engine. The crankcase wouldn't build pressure unless you plugged the hose in that last picture posted above.

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post #7 of 11 (permalink) Old 08-14-2013, 01:56 PM Thread Starter
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thats what I was lookin for someone had already removed the hose, and i didnt see it sticking out had to look closer, well will have to get a vent for it
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post #8 of 11 (permalink) Old 08-14-2013, 02:34 PM
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The crankcase is vented from the front head to the front part of the surge tank. There is no PVC system like on a car. I don't know why motorcycles never used that system. There is a lot more vacuum coming from the manifold than what little is in the surge tank. My '85 Goldwing was designed the same way, only a lot more complicated. There were 18 separate parts in the crankcase venting system. When I got done with it there was one, a piece of heater hose connected to the vent fitting on top of the engine, and ran across the top of the engine to the other side, and down under the bike. The aforementioned "road draft tube"

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post #9 of 11 (permalink) Old 08-14-2013, 02:57 PM
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I do not believe you will ever see a Positive Crankcase Ventilation system on a single carb per cylinder configuration. The best possible would be plumbed into a common intake plenum, like OEM 750.
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post #10 of 11 (permalink) Old 08-14-2013, 06:31 PM Thread Starter
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I just wanted to know where the vent port on the engine was, lol searched all over and didn't see it in all the normal places, the previous owner must have removed it, installed pods and rejetted yesterday, and noticed I didn't see a vent port anywhere lol. although your local auto parts store sells a really slick rubber elbow that worked great its for a ford vacuume port reduces the size down a little smaller and the larger end fits snug on it
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