Problem:
Faulty Gas Check Valve.

Fix:
Replce this Gas Check Valve.
Location:
Under rear body plastic near the filler neck of the Gas Tank.
This valve is a bit to get out, so your rear Body Plastic will need to be removed.

The Gas Check Valve is to allow Air into the Gas Tank, as it is a Vacuum hose.
This is not a Vent Hose to allow Gas out.

This Gas Venting has been reported to be a problem on some 07 & 08 BF750's.

 

A faulty gas check valve might have been it.
But also a good valve can also cause that, too.

There is little more insight to this as following:
Its main job is let air into the gas tank so that tank does not collapse as fuel is being used.
Its another job is to let excess gas fume pressure built inside the gas tank to escape when it reaches around 4~5 psi so that the plastic fuel tank would not expand too much and rupture.
In any combination of following conditions, the liquid fuel would be coming out from the handlebar area.
> Fuel level is high.
> Riding in hilly terrain.
> Weather is hot or very warm.
> Engine has been running for a while.

So, before you yank out the check-valve from your quad, using a Mighty-Vac (hand operated vacuum pump with a gauge), check to see at what psi does the valve open. If the check valve opens at less than 4 psi, I would say it is faulty.

Why handlebar area?
Because the fuel tank vent line is routed all the way to there exit is there (via tube frame).

 

why does this happen.. is there a fix to keep it from leaking gas??

 

It is not a Vent Hose, it is a Vacuum Hose and it is only to let air into the tank.
I've done allot of research on this gas check valve, it is a one-way only design. If any gas is venting out from under the handlebars then the gas check valve has failed. All of my Brutes/Prairies have run high pressure in the gas tank.
The last two Brutes I have owned did this gas Venting, the 08 was worse. Even with just two bars on the gas guage showing, I was venting raw gas.
I replaced the Gas cap 1st, thought it fix it for a long weekend ride but on day three the gas started venting again. After replacing the $23.58 gas check valve and running my Brute hard, in 4x4low allot & getting the Brute to really put some heat out-no Venting at all.
Before it would vent at either a full tank, half tank, low tank or just while out crusing up a long hill climb in 4x2H it would spit out gas right onto the the air-cleaner lid.
Hasn't vented any gas at all in the last 250 miles since the Gas Check Valve hasbeen replaced and the other big plus is my MPG has gone way up..

 

<div class="FTQUOTE"><begin quote>Originally posted by: bfb750BF
It is not a Vent Hose, it is a Vacuum Hose and it is only to let air into the tank.</end quote></div>

Exactly, it is letting outside fresh air "vent into" the tank as vacuum is created as the fuel being used. And the excess pressure has to go somewhere and that's where it goes out through. But a faulty one will let it out at the lesser pressure.

 

I have had this happen about 4 times with my brute, so is this something that needs to be fixed or is this natural? I'm confused. please more on this. I even took it into the dealer and they had no clue why, they did ajust for high elevation riding which is mainly what I do. but I have had it happen since then.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Hayashi

A faulty gas check valve might have been it.

But also a good valve can also cause that, too.

using a Mighty-Vac (hand operated vacuum pump with a gauge), check to see at what psi does the valve open. If the check valve opens at less than 4 psi, I would say it is faulty.
</end quote></div>

I already explained that it can happen on either good or bad check valve, and why it happens in my very first post.

If the valve opens at higher than 4-psi, the fuel would only when the fuel tank internal pressure is higher than 4-psi with some of the certain conditions I mentined like full tank, etc.

If the valve opens at less an 4-psi, it is bad. The fuel would come out MORE
OFTEN than when the valve is good (when it ONLY opens at higher than 4 psi).

Find out at what psi your check valve opens.

You may say why not somone design a check valve that opens at much higher pressure so that fuel never comes out. Well, that's because the plastic fuel tanks used on quads can't stand high pressure. So, the excess pressure built up inside the fuel tank has to be relieved in order to PREVENT rupturing of the tank.