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fuel supply questions

ipo

ipo

Tuned and Synch'ed
Joined
Jun 13, 2009
Messages
50
Location
Toronto
Hello everyone, I have a couple of questions regarding the fuel supply in my Griso:

1. From a sitting position, the gasoline tank has 2 small outlets at the back. I know the left one is for a breather line but I'm not 100% sure about the right one. Is this latter for the hose that contains the pressure valve (what looks like a small light gray doughnut) and it eventually attaches to the canister at the bottom of the bike where the carbon filter is housed?

2. Does this fuel hose actually carry fuel or only vapors? (I ask because it seems to be the line in the schematic for the fuel vapor recovery system, tab 61, in the parts manual for the Griso).

3. This last question requires a bit of explaining and it's physics related. When I removed the fuel tank I did not empty it first but no gasoline was being released from either outlet. Then I placed the gas tank upside down and I removed the fuel pump to check it. No gasoline was flowing out of the tank before I removed the pump. But as soon as I re-attached it, gasoline began to spill from the right outlet even though the tank was still upside down. I do not understand why. Is it because when I re-attached the pump air found its way into the tank? Is it because under normal operating conditions the pressure in the tank is different from the outside pressure? Is it because I did not seal the pump properly? Did I do something wrong and I made the hose deliver fuel to the carbon filter instead of vapors?

Your help is appreciated.
ipo
 
I believe one of the two lines is the tank breather and the other is the overflow drain. There is a small drain hole under the cap next to the filler hole for if/when you spill gas when filling up. This drains down thru the tank and out the back.
The drain line should not go to the canister (but neither should the other in my opinion). My Griso developed an issue where it would appearently pressurize the fuel tank when it got hot in the sun. This would cause the drain line to somehow drip fuel. The solution was to remove the canister and the one way valve in the vent line. Now it drips no more.
 
When you say that "the drain line should not go to the canister...", do you mean that that line does not attach to the right outlet or that, in your opinion, it should not attach to the right outlet?
 
I do not remember which is which, but if you blow air thru them you will find that one of the two is a vent for the air space inside the tank (to allow air in to the tank as fuel is pumped out and burned) and the other goes to a drain for the area under the filler cap for in case you spill fuel while filling up (or presumably also in case water gets under/inside the cap. This second line to the drain under the cap should not go to the canister. There have been cases (including my own G11) where as they came from the factory/dealer these lines were not done correctly.
Personally I removed my canister and the one way valve that only lets air go in to the tank to keep pressure from building up in the tank.
I hope that is easier to under stand.
 
From a sitting position there is, as you said, a small hole under the cap which is connected to the left outlet from the inside of the fuel tank. On the outside, a breather hose is connected to the same outlet and it is open at the other end, so this explains what you were saying about overflowing the tank and having a way to dispose of surplus fuel.

The right outlet is the one I'm concerned about because when I removed the tank I think the hose came off on its own. I've checked the schematics for the bike but it is not quite clear if the hose that has the pressure sensor and eventually attaches to the canister is the one that should be connected to this right outlet.
 
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