Your Tech is full of crap. This is the reason for the check valve: it's to create a sealed system, same as on a car. In order to meet the current EPA emission limits, the manufacturers not only have to limit the emissions from the exhaust, they also can't allow any gas fumes to escape from the system. The check valve is a one-way valve only, so it can't "bleed off" excess pressure as your tech has said.
The fuel pump supplies all fuel to the carbs when the engine is running. When fuel is pumped out of the tank, air is pulled in through the check valve to replace the missing fuel. At no point is a pressure build-up designed to "push" gas to the carbs. The only time you have pressure in the tank is when the fuel becomes heated from engine and exhaust heat. This effect is at it's greatest just after you shut the machine off. The heat from the engine and exhaust will flow around the tank, heat the fuel and cause expansion and thus pressure in the tank. This pressure can easily exceed 3 psi, which is why some machines end up with gas in the oil.

 

Cool. About time we got an answer that makes sense. I didn't even think about the emission control crap. My 650 is----as you would say----not treehugger friendly!! My fuel tank is vented, my exhaust is bored out, I'm cramming more air and fuel through the carbs and I have big lugged mud chucker tires. Anyone want some alfalfa sprouts on kelp?

 

I believe it is axactly like Newbettle said,

That it will bleed off after 3 pounds pressure and will let air in under 3 pounds. 3 pounds will lift your cap but you usually have your hand over it and your fingers around it so it is nothing. Plus it blows the dirt away apon fill up in the woods.

Of course they have to have it vented or it would blow up and there is NO way Kawi would let it get over 3 pounds because of that, Whoever thinks that is full of CRAP, it would be a explosion waiting to happen. If the pump puts out 3 pounds then they have to keep it EQUALIZED but still have a check valve to keep gas and fumes in the bike. A 3 pound check valve must have been the ticket.

I like the idea that no gas is going to escape under any conditions, flipped over on her back or on her side in a brook. There is no problem with your vented and pressurized system, as long as you store her with the petcock off. A very good and probably the main reason for this type system and as somebody said, no gas fumes either.

Like Newbettle said, if a piece of dirt gets in your carbs and with the 3 pounds pressure in your tank you have a good chance of leak by. There is NO chance if you turn your petcock off when stored, no pressure can push it by.

Tear your stock system off if you want but it's not necessary, there is nothing wrong with your quad. They put an auto shutoff on the Brute because of people not able to grasp the concept of shutting of the petcock or why they should have to.

I might be dumb but I'm not stupid,

 

hahhah, I bet you have a "Tread Lightly" sticker on the rear too [img]i/expressions/face-icon-small-smile.gif[/img]

 

1. The check valve is just that: a check valve is by definition a one-way valve. It will NOT bleed off any excess pressure in the tank, it will only let air into the tank.

2. "The valve will let air in when the tank is under 3 pounds pressure"??? How does a valve open and let air pressure into an already pressurized tank?? Short of having an air compressor hooked up to the fuel tank, this statement is against the laws of physics.

3. FYI- the fuel pump runs at 3 psi. The inlet needle in the carbs can hold back more than 7 psi.

BTY - rather than removing the check valve and running a line up to the steering stem like some have done, I took the valve apart and removed the one-way flapper, put it back together and stuck it on (lazy man's fix, lol). The valve only works in one direction, it can't work in two directions.

 

Wow then I took the super lazy dude route [img]i/expressions/face-icon-small-smile.gif[/img] I just unplugged the hoses and added a fuel filter. Plainsmans Vent

How did you get the stock checkvalve apart, did you lift 2 retaining tabs and slide it out, or do you cut the ziptie and pull it out of the assembly. I cut the zip tie and just pulled but it wouldnt come out. Since the hose terminates in the the rear frame, where does it suck in air from, did you find that?

Thanks much Nova.

 

Just so people know, the shut off valve does not work, lol. I've had three Kawi V-Twin quads and they all hydro-lock, gas in the cylinders. The shut off valve may work when sitting still in a garage or outside. When you transport the quad for many hours the shut off valve doesn't seem to work to well.

I'll be doing something to my vent line this spring, I experienced to many hydro-locks so far, dont want any more.

 

[quote]
Originally posted by: Plainsman
How did you bypass yours?[


Just take both hoses off that come in and go out of the check valve and you will have to use a short piece of hose to use for the length of the check valve and just bypass around check valve. Get a couple of hose connectors and connect everything up and a couple of cable ties. Yours should be vented into the frame, I didn't change anything there and I just left the check valve bolted to frame. You should be good to go, it didn't take very long to do.

 

Novakaw, I did the same thing not 10 minutes ago. I took out the check valve to see how the hell it worked. When I blew in it towards the tank, no problem. Then I turned it around and blew away from the tank, nada. I blew like a hooker on Saturday night and still no go. Then I washed it off and noticed you can take it apart. I took it apart, took everything out of there and put it back together and gave er another go. Free flow in both directions and it didn't even cost me $2. In your face Plainsman!!!!LOL!! HAHA!!! Now all I need is a new gascap and I'm good to go!!

If I could blow through it one way and not the other, I guess that blows the 3 pound theory all to hell. Plainsman, let me know how you do on the tank as I am good to go for a cap. I'm already ahead $2!!! [img]i/expressions/face-icon-small-happy.gif[/img]

 

Oh man, LOL.

So if you can blow both directions, there isnt going to be any pressure building. Blew that theory out of the water IMO.

You know on that valve, you can cut the zip, then pull the piece back a bit, does it pull off there? Or did you unbolt the filter bracket ect? Tell me how you took it apart, you cheapass. lol