Modifying gas tank filler neck?

[pago cruiser]

As everyone is aware, getting the last 1/2 gallon into an IS tank is a pita.  It literally takes mw 15-20 3/4 to 1 second bursts of the gasoline pump to get in that last 1/2 gallon.  And rushing the process results in gasoline overflowing the tank...  There has to be a better way.

I think that the reason it occurs is that the filler neck extends down into the tank 2.5" in the front, and about 2" at the rear.  Once fuel is "stuck" in this tube, you have to wait for the level "in" the tube fall to the same level as the tank itself - WITHOUT a vent.  While I'm pretty sure it is for slosh control, this in maddening.  I have never seen another bike with this particular goofy idiosyncrasy.

I'm getting ready to paint my solo Valk, and am thinking about drilling maybe (2) 1/4" holes on port-starboard sides of the filler neck, down about 1/2" into the tank from the gas cap seal surface.  I'm thinking the port-starboard orientation would cause the least affect to the anti-sloshing design from Mother Honda, but also provide some venting to aid fuel "leveling" process.

Any thoughts?

[bentwrench]

Be careful,cold gas from an under ground tank expands considerably.I think you might cause an overfill condition that could cause  fuel to pee from the vent hose.

[Jess from VA]

I often take the time to top up the ISs, but only when I get lucky enough to have a slow feeding pump.  Sometimes the feed is so hard and fast it is like air refueling (and just not worth it).  But really, it's only when I'm on freeway tank-to-tank trips that I feel an actual need to really top up.  This is an East vs West issue; out East you have to really work at running out of gas.  

And I tend to (re)fill at the same my buddies on 5-5.5gal tanks do.  I can go farther than they can, but I can't wait until they need their 2d tank either. 

I have done a little experiment with filling to tip-top.  I'll go about 65 miles before I lose my first led gas gauge bar.  Other times half that, which is consistent with the idea that taking the time to get it full to top amounts to about a half gallon of fuel.

I have no opinion to offer on drilling the neck.  Other than to avoid sparks.  

[Farther]

Punching a hole to facilitate venting the vapor space has been discussed before.  I am not aware of any down side.  Although I think drilling may be a bad idea because of the metal debris from the drill bit.

[Pete]

1/4 inch is to large, if you decide to do this use 1/8 or smaller.
You do not want gas escaping the holes, just air.

Drill below the lid seal at the level you want the gas to fill to.
Leave some air space for gas expansion and for the tank to breath.

[98valk]

there already is an existing hole in the fill neck. there was a mod posted yrs ago about enlarging the hole and the correct size to do it.

[gordonv]

Actually, read the manual, you are only suppose to fill to that filler neck, NOT up it. That is a full tank. Any more, and you are now over filling.

I do over fill, but only while still on a ride and am going to travel at least another 25-50 miles.

Stand the bike upright, and squeezing gently, fill it up slowly. Close it up quickly and get moving asap.

[Bighead]

My question is why worry about that last 1/2 gallon you "can" squeeze in? How much further can that get you 15 miles or so? Too many things in life to worry about other than that IMHO.

[dago mooserider]

there already is an existing hole in the fill neck. there was a mod posted yrs ago about enlarging the hole and the correct size to do it.

What he said.... enlarging the existing hole a little works wonders.

[98valk]

Mark T site
http://www.horseapple.com/Valkyrie/Tech_Tips/Burping_Brunhilda/burping_brunhilda.html


Had to remember back, I kinda did this mod yrs ago, but I used an awl and just worked it in the hole to enlarge the hole. no metal shavings. like mark states its soft metal.

[John Schmidt]

If I want to get the last few ounces in because I'm on a long ride, I just straddle the bike upright and rock it gently as it gets near the top. It will burp down so those last bits of gas will go in. Most of the time I don't bother, not worth the trouble and you don't really gain that much.

[DK]

I enlarged mine last year with a mallet & a brass drift. No sparks.

Mainly lets me fill tank quicker.

[sandy]

I punched mine out with an ice pick and wiggled it to stretch the hole. NO drills due to shavings.

[R J]

I punched mine out with an ice pick and wiggled it to stretch the hole. NO drills due to shavings.

This is the way I opened up the vent opening on MGM in 1999.

On the right side of the gas tank opening, setting on the bike, is a small hole.  stick your ice pick in that hole and waller it around.  That piece of material is very soft and will expand out quickly.   Filling problem is solved.

[pago cruiser]

WOW!  Ask a question I could not find an answer for and get answers and pics...   

Thanks guys.  I commute about 100 miles/day round trip, so am usually filling up every other day, as it is seldom I will push 200 miles on a tank on reserve.  If I run around at lunch for stuff or ride to work meetings during the day, I am sometimes filling up EVERY day.    That extra 1/2 gallon is really handy.   

I did not look close enough to see the maybe 1/16" hole up near the top on the right front side.  Just went outside to confirm on my Valk Hack.  The solo Valk is being painted right now, so no problems with drilling/fumes/removing filings.

Thanks all for the replies.