Installing the Krankvent from ET-Performance

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Written by Pat Martin (USAFRETIRED)   
Tuesday, 26 July 2005

[Editor Note from GRAM: ]  I have used the Krankvent for a number of years now, and have been very pleased with it.  Subsequent to an offer from the manufacturer for a unit to review, I asked Pat to install it on his bike and provide the basic installation instructions below.  It is more expensive than using a PCV valve or an external air filter, but provides some real benefits with regard to endurance and maintaining best head vacuum.

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ET-Performance has adapted thier very popular crankcase vent (Krankvent) for use with the  Roadstar.  A lot of us are currently using PCV Valves or external air filters to provide this functionality when we change out the stock air kits on our bikes.  Some are even using open tubing run to the ground.  Each of these serves its purpose by allowing the excess pressure to be relieved from the heads and crankcase during a normal combustion cycle.  In the stock configuration, this pressure (and its accompaning oil blow by) are vented to the air kit, which sends the air and oil into the carburetor for consumption in the normal air/fuel mix. 

The problem is normal for combustion engines, and occurs in the heads above the valves and below the piston rings in the crankcase.  When the pistons are moving up and down, they are drawing in and expelling air into this "non-combustion" area. Some of this pressure is caused by the normal movement of the piston in its cylinder, some from "blow by" that escapes around the sealing ring of the piston.  This creates a pressure in the crankcase that can sometimes cause seals to leak. It also creates an energy in the form of air pressure that the pistons have to work against.  Every combustion engine needs a way to relieve this pressure for best performance. 

In the stock Road Star configuration where venting is sent to the carburator, the oil "blow by" products in this vent lead to a general "gumming up" of the carburator from accumulation of the oil blow by .  Although not harmful to the carburetor, this leads to dirty carbs that occasionally need a good cleaning to remove the accumulation and optimize thier performance.  Occasionally, in particular when engine mixes lean toward being too lean and thus building up excess heat, this can end up being a messy job as the oil blow by tends to get "cooked" into the throat of the carb by excessive heat.

Providing an aftermarket crankcase ventilation method for your bike helps to keep the carburetor cleaner, and in particular with aftermarket air kits, avoids the problems associated with oil leakage (from the open elements of the aftermarket kits) onto the engine below the air kit and oil spray from the same source that tends to spread itself onto our nice shiny chrome parts in the wind behind the air kit.

In the case of the Krankvent, there are a few other benefits that are worthy of consideration:

The Krankvent is designed to let the pressure out of the engine (piston coming down), while limiting the amount of air that is allowed back in (piston going back up). This creates a partial vacumn inside the engine which reduces the force (internal air pressure) that the piston has to push against while returning to its starting position for a combustion cycle.

The folks at ET-Performance claim the Krankvent will last forever because of the material it is built with (we have heard of no failures). They also claim that higher horse power can be obtained, piston rings seal better, and emissions are reduced. The Krankvent is very simple to install, so let's take a look at the kit and installation.

  • We can see what is included in the kit in this picture. Installation instructions, the Krankvent, plastic ties, and two hose clamps.

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  • You want to make sure that you selected the correct hose to install the Krankvent. We are going to install it in-line with the hose on the rear head, on the right side, and towards the front of the bike. The arrow in the picture points to the correct hose.

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  • After you select where you want to install the kit, cut the hose and install the Krankvent. Insure that the Krankvent is allowing air to escape away from the engine before installing. You can do this by blowing through it to see the allowed direction of air flow. Secure it  with the two supplied hose clamps, and tie it up with the two supplied plastic ties. Installation is complete as seen in the picture. Keep in mind that my hose is routed to a small filter on the left side of the bike. Your hose might still be routed to your air cleaner which will require a different location to install. This is a very simple item to install.

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Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.


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  Comments (9)
Krankvent
Written by SaltyJack, on 11-11-2012 15:30
I came across this and I guess I am to believe that its not a real good idea to install one. Correct? I have this oil accumulate just behind the rear cyl next to the plug for adding oil. I just had an new intake manifold installed and mentioned the oil thing to the mechanic,he later told me that he changed the rubber or what ever type seal on that plug and it should do it. Ive nver had to take the bike out for a good run since having it done a week ago. Just fishing here for other ideas..
crankcase vent
Written by hrdbrgn, on 02-09-2012 07:37
null 
So I have my hose removed from the air box and just routed elsewhere to keep oil off my bike and out if the Carb. The hose is open w no pcv valve or Chk valve on it. So am I sucking dust/moisture etc...into my case or do I need to put a filter/pcv valve on it?
Bad News?
Written by USAFRETIRED, on 04-10-2010 22:02
"I was sucking air/moisture into the engine" 
 
This device is connected to a hose which is a "vent", which in stock location is to the air cleaner. Meaning it is open to air/moisture. If you reroute the hose to one of the aftermarket little filters, is still is open to air/moisture. By removing it, you did nothing to change the induction of air/moisture.
IMHO Krankvent is Bad News
Written by Randysgym, on 12-31-2009 06:02
I ran a Krankvent for 2 years before tearing down my engine for a 113ci big bore. I found numerous case bolts that were corroded; couldn't figure out how. Then, when I got the new engine running (with all new ss bolts), I accidentally put the Krankvent in backwards, and got oil leaking out/around several case bolts. This told me that, with the vent 'properly installed', I was sucking air/moisture into the engine. I started to tell my performance parts supplier, but all I had to do was say "Krankvent" and he told me to get it off my engine or he would void my new parts warranty... I did.
Failure
Written by Van, on 10-20-2009 14:01
While servicing my bike, I thought I'd check the function of the Krankvent I installed a few years ago. 
Much to my surprise, it was open in both directions. Air flowed both ways. 
I guess they can and do fail. 
Never saw any improvement while it was working properly anyway.
Krankvent
Written by seadevil303, on 10-23-2008 22:54
Have a 2003 RS*. Put one on my bike about two years ago. Did'nt notice a change that i could tell but read about the neg. pressure it puts in the cranckcase so that the rings will stay expanded at higher R.P.M. in the cylinders. This one works as long as you do a regular cleaning to it, it gets the oil residue that the carb would. So keep it where you can to it.
Check This Out
Written by Brutha, on 10-27-2006 08:10
I'm not saying anything one way or the other. But I found this interesting. I don't know how to create a link but if you copy this and paste it onto your address box and hit go it works. 
 
www.nightrider.com/biketech/crankvent_test.htm
Krankvent
Written by Brutha, on 10-27-2006 07:20
I've noticed the oil in my stock air filter and am planning on rerouting the crank case vent hose as soon as I figure out where I want it to go. This part is simply a check valve. The packaging is attractive. After comparing the pricing I'll decide whether an alternative source is better. 
 
Check valves do fail although you typically wouldn't know unless you try and force pressure against the seal. If it failed in this application you would simply have ambient air pressure as resistance and no checking function. The same as you have with an air filter attached. The carburetor supplies some vacuum.
Alternative hose routing
Written by GRAM, on 08-30-2005 11:56
As an alternative to the way Pat routed his hose for the krankvent, I found that I was able to route the hose back along the top frame member of the bike, under the rear of the tank, then down along the frame post that is just at the rear of the tank. 
 
I ran it through the ties downs on the left side (facing toward front of bike) of that post, all the way to the ground. This is the same path used by one of the line for the gas tank vent, which I removed. Removing the gas tank vent valve left just enough room for this line to be passed through the same area. At the bottom of the frame, there is a metal loop attached to the frame that was designed to keep the gas tank vent from getting into the rear suspension and tire. I ran the line all the way through that loop.

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