gas cap

[drtaco]

hey guys took the bike out on the main highway again, (getting it ready to get my title and plates tomorrow, going to drive it for a long distance of 15 miles tomorrow:) to shop to get tires.) so I filled it up, thought i left level just above the ridge in middle of the tank. after the ride(3/4 of a mile) when i parked it, i did a few things, noticed what i thought was 'another' oil leak on the floor but it had come from the fuel cap. when i opened it fuel blew all over, then the  level was still a little over the ridge? so doesn't it vent thru the cap (my original drip?), why was it so eruptive (heck of a vacuum cause that?, back pressure from fuel pump?). if it doesn't vent properly it will effect runablity i would think (vacuum would keep fuel from flowing) ? any ideas

[QBS]

V design defect from the get go.  He who over fills his tank while said tank sits over a hot engine is often surprised with said tank regurgitating fuel all over just about everything.  My take is that fuel in the lower levels of tank is gasified by engine heat and displaces fuel out the top.  Side stand use aggravates the problem by requiring an even more circuitous path for the vapors to escape through.  I think that there is no excuse for this defect.  It certainly represents a very serious fire hazard.

[fret not]

The fuel will expand significantly as it's temperature rises.  It doesn't need to actually become a gas for this to happen.

I know that if you fill your tank with cool gasoline and let it warm up the tank can overflow.  Most tanks for filling stations are underground and consequently insulated from the outside temperatures, so in the warmer weather the fuel they deliver  will be cooler than the ambient temperature where your vehicle is.

[Rikugun]

This sounds a lot like what Tiger and others referred to as the Vision Volcanic Eruption. Some carefully located holes in the lip of the "filler neck" area can eliminate this phenomenon.

[Tiger]

This is a PITA...but a real easy 'fix' ;)

You need a drill/1/8" drill bit and a magnet.

Remove the gas cap...look down the opening and you will see a shoulder, with cut outs, to locate the gas cap...at about 1 o'clock and 7 o'clock you need to drill a hole through the shoulder and through the down tube wall into the tank...VOILA, job done.

This will give you a couple of plus points:

1 - These two wee holes allow the trapped air to escape as you fill up and stop the gas eruptions from happening... 8)

2 - You can actually get a wee bit more gas in to the gas tank at fill up time. (I used to fill mine right up to the gas cap locking shoulder with NO eruption/leaking problems)... 8)

I take no responsibility if you blow yourself up or damage your Vision, so, please take all precautions to avoid any catastrophe's occurring during this 'fix... :o

           8) ....... TIGER .......  8)

[drtaco]

thanks guys, tiger as soon as I get the bike back from the shop with new tires, I am gonna do your suggestion, talked to legal department and they said your disclaimer was valid and if I proceed it would be complied negligence and if something should go wrong it would 'suck to be me' :laugh: 

[drtaco]

tiger I may still try your idea, but I just was bugged about how the tank vented. had to be thru the cap so I started to take it apart. when taking the 2 allen head bolts out be careful, the locking mechanism has a very small spring between cover and first slide also it might be good to mark orientation of how parts come off. once the locking pieces are off (put them and other parts you will be taking off in bowl of white vinegar it works on brake parts too!) pull the round housing off(this holds large main spring which stayed in place for me) looking down at the gas cap (just like you have been taking it apart) you will see to the side of the locking mechanism a rectangular chamber, first in this chamber is a brass locking clip, it has 'legs' that come up the side of the chamber, I bent these in slightly to remove it. second (or next how ever this is flowing) , at the bottom of chamber there will be a flat brass plate with three holes (sort of remember orientation ) pull this out DO NOT turn cap upside down and smack. after you have lifted out the plate you will see that there is a small steel ball and to the side of that some type of 'fabric' piece. to remove these you may need to flip cap over take off plastic cover. with the cover off you can look down on the maze that is the 'vent' path (god I hope I am right I hate when I am wrong) it starts in the pie shaped area(oh yeah look for two small holes in the pie area, this is where to push out ball and 'fabric') look for small cutouts in the ridges and how it goes to each section till it goes out to the outer edge. clean these 'cutouts', holes and also on the other side of cap at bottom of rectangular chamber another small hole in the side. then clean again use compressed air also. putting back together one thing that you might remember is holes on little flat brass plate should line up with ball and 'fabric'
now I tried to explain it as if you could see those parts, when doing mine I couldn't it was corroded up. I did not re-install the small  ball nor the piece of 'fabric' yet , going to see how it works. hope this helps if not' oh well