Getting Air Out of Neck of MKII Gas Tank Faster?

[GolfVenture]

I really like the idea of some 2nd Gen owners punching holes near the neck of their tank to get more gas by getting rid of the trapped air.

 

While in the process of cleaning my fuel system on my 89 MKII, the punching hole technique just won't work for the MKII.

 

I kept saying to myself, got to "think out of the box". I kept staring at the neck of the tank, then a thought came to me. The tank already has a built in venting system at the very top of the tank. But it is connected to the overflow hose that ends near the bottom of the frame.

 

So as one puts more gas in the neck of the tank, the extra gas has to push the air out the overflow to the bottom of the frame. This is a very slow process

 

The ? is, would the extra gas in the neck push the air out faster, if the there was an air outlet above the neck of the gas tank. This I do not know.

 

If the answer is Yes then 2 possible solutions:

 

1) In the picture you can see the vent hose. Maybe one could T off from the hose and then bring the new hose section thru a hole in the square rubber unit around the gas tank neck. Then on it a valve,so that when you gas up you open the valve then close it.

 

2) No valve and if the gas pressure build up and over flows most of it will go down the main over flow hose and if any gets thru the T section into the square rubber unit, the square rubber unit has its overflow hose.

 

Any thought?

 

Or are the 2 levels of gas the issue? The air pressure of the gas in the neck vs the air pressure of the gas in the main tankl?

Edited April 29, 2013 by Golf&Venture

[MiCarl]

You do realize the whole point of the Yamaha arrangement is so fuel doesn't dump out when it warms up and expands?

 

Is the risk of spilling fuel really worth getting an extra pint in there?

[Prairiehammer]

I think you are potentially creating a risk over a non-issue.

[GolfVenture]

You do realize the whole point of the Yamaha arrangement is so fuel doesn't dump out when it warms up and expands?

 

Is the risk of spilling fuel really worth getting an extra pint in there?

 

Yes, I realize that.

 

I just like input into my idea if it would work or not work and why.

[Flyinfool]

To tee off of the vent line will help a little but not much. The limiting factor is the size of the hole where the tube goes into the tank. By adding the Tee all you are really doing is shortening the length of the overflow tube to get slightly less parasitic drag from the tube length.

It would be a lot of work for very little gain. The amount of gain may only be theoretical in size.

 

And as has been mentioned, you will only pick up ~5 miles worth of gas.

It would be a lot easier to carry one of the small sealed gas bottles with a quart or half gallon of emergency gas in a corner of the saddle bag. That will at least get you 10-20 miles.

Then there is the safety issue of removing the expansion air space that was designed into the gas tank.

[Condor]

With the rule of riding 150 +/- miles and tanking up again, the question is why, and who cares?? If you don't feel secure in that you need more fuel carry another half gallon in a spare bottle. REI sells a nice one. I just stick the fill nozzel in the tank and when it shuts off it's enough, and ride another 150miles.....

[dingy]

The purpose of this line is to allow air to get back into tank as it is used, not to vent tank.

 

The vent line passes thru a one-way valve near the tank (just visible in picture in 1st post). This valve will not allow fuel thru. Purpose is to shut tank flow off thru vent line in case bike is on its side. By putting a tee in near the tank, the safety usefulness of this valve is gone.

 

Think wreck, bike has your leg pinned under it, and tank slowly starts leaking a puddle of gas. Bet you wish you left it alone.

 

 

Gary

Edited April 29, 2013 by dingy

[GolfVenture]

The purpose of this line is to allow air to get back into tank as it is used, not to vent tank.

 

The vent line passes thru a one-way valve mid way down the frame. This valve will not allow fuel thru. Purpose is to shut tank flow off thru vent line in case bike is on its side. By putting a tee in near the tank, the safety usefulness of this valve is gone.

 

Think wreck, bike has your leg pinned under it, and tank slowly starts leaking a puddle of gas. Bet you wish you left it alone.

 

 

Gary

 

I didn't know that about the 1 way valve. Thanks for the correct explaination Gary.

[timgray]

If you want more range, do the needle shim mod. 180-200 miles per tank at the same point where I would have 150 is a wonderful thing.