Want to get an extra 2 litres in a standard GS tank?

[Goosey Gander]

It's very easy to modify a GS tank:-

1) With the tank in position remove the filler cap assembly and disconnect the two drain hoses, taking care not to drop them into the tank.

2) Pull the black oval overflow/ vacuum release case from its mount and replace with a 2 inch length of fuel hose. (This acts as a snorkel and will prevent fuel draining but still allows the vacuum to release).

3) Drill several holes in the collar of the fuel filler cap directly below the flange to allow for air displacement.

4) Replace drain hoses (it doesn't matter which way round) and re-assemble.

eh-voila! Now you can fill the tank to the brim. I have a photo of the drilled filler cap assembly on my website.

Goose
www.gooseontheloose.com

 

[(RIP) Yosi]

Cracking web site, mate!

Excellent web site. One of the best I've seen. Don't know were you are now, but best luck. Yosi

 

[guitarman]

I remember spending an extra 5 minutes at a fuel pump persuading an extra litre or so into the tank (past the lip of the fuel filler tube) and was rewarded with petrol peeing out the overflow pipe. Is this mod going to stop that ?

Cheers

guitarman

 

[Sleepy]

Extra Fuel....

I've done this mod, and it does overflow..!! so I can only fill it up to the brim if I'm going to put a few miles on straight away.

 

[guitarman]

That's exactly what I had to do......

 

[Goosey Gander]

This mod works, definately

Guys

This modification does work if you do it properly.

The fuel overflow 'thingy' is about two inches from the top of the inside of the tank. If you pull this off (it's easily replaceable) and attach a 2 inch piece of fuel hose (effectively a snorkel) your overflow is subsequently two inches higher.

I did read a thread a few months back by someone suggesting that drilling holes in the fuel filler neck is all that is needed. This is wrong, drilling these holes is necessary but only to allow for air displacement.

Give it a whirl, it's a ten minute job.

Goose.
www.gooseontheloose.com

 

[guitarman]

OK Goose, I'll give it a go as I could certainly do with a couple of extra litres. Would make Sundays in France a little less fraught.

Cheers

 

[Howard Millichap]

If you fill up with the bike upright, then when the fuel reaches the brim, shake the bike side to side slightly whilst topping up. This will displace some of the air trapped by the brim, thus allowing more fuel into the tank. No need to drill anything. Don't ask me how much extra this method allows in. It's a bit tricky measuring while your shaking the drips off!!

 

[Malky]

If you fill up with the bike upright, then when the fuel reaches the brim, shake the bike side to side slightly whilst topping up. This will displace some of the air trapped by the brim, thus allowing more fuel into the tank

Guys,
This is exactly what I do on my R1100GS. However I think what others are saying is that you can get even more from the tank by raising the height if the overflow and allowing air out via the hole in the cap ?
I have found that the tank will overflow sometime after filling to the brim. This only happens on hot days when the expansion of the fuel is enough to force fuel out of the overflow. I guess this is why BMW have deliberately left air in the tank.
Question : Why bother with the hole in the cap ? Maybe I am missing something but if the overflow is raised then surely that would let the air escape ? I can't imagine there is a valve that only lets fuel escape but not air.

Interested in the views of those of you who have dabbled as opposed to my theorising

BTW Goose cool site !

Cheers

 

[Goosey Gander]

Malcom

can't remember for definate as it's a while since I've had the tank apart but I'm sure the overflow pipe runs through the fuel pump which may not allow air displacement when the engine isn't running. This is only a theory based on the fact that the engine will not run if you block the overflow pipe.

Tho holes in the filler neck also allow you to fill up quicker.

Goose
www.gooseontheloose.com

 

[Malky]

Goose,

cool. I can see I may have a poke around when I'm replacing the fuel filter.

The most I have ever had from a tank was 226 miles.
I don't have a note of the volume but did calculate the consumption as 56mpg therefore that equates to 18.3Litres I squeezed in.

So I guess I can look to squeezing in other 24 - 18.3 litres.
But that would be 5.7 litres ! The tank is 24L ? micapeak.com says so.
At 56mpg that would give me another 70miles.

Well those numbers look impressive, however I only once got 56mpg on a 600 mile trip the 1st day I owned the bike and was being very very conservative whilst riding.
Of course I now thrash the hell out of it and can drop from my usual 49mpg all the way down to 45mpg.

I think I'll post the consumption stuff elsewhere - I'm sure I saw a thread.

Feel free to challenge my tank volume as I cannot believe with 56mpg I could have a range of just short of 300miles.

 

[Sleepy]

The story so far...

1) With the tank in position remove the filler cap assembly and disconnect the two drain hoses, taking care not to drop them into the tank. done that..

2) Pull the black oval overflow/ vacuum release case from its mount and replace with a 2 inch length of fuel hose. (This acts as a snorkel and will prevent fuel draining but still allows the vacuum to release).

no black overflow/ vacuum thing found.... see pics. Is this a different layout?

 

[Sleepy]

another pic

........

 

[Goosey Gander]

Sleepy

yes, that's definately diferent from mine which has only one tube running from the filler neck to allow for overflow. I have a photo under 'Technical' on my website.

If you can get the plastic 'unit' off without causing damage attach 'snorkels' to both tubes and see what happens.

Sorry I can't be more specific.

Goose
www.gooseontheloose.com