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bottomless tank on my 94 VFR750?


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So I stopped to fill the tank on the Viffer yesterday. The light had not turned on yet, so the manual tells me that I had about .92 gallons in there. And I added 5.20 gallons on top of that.

Smart readers will notice here that the OEM manual says the tank is only 5.5 gallons in total.

And yet, as I added the gas, it never REALLY got up to the top. It would fill up to the inner ring that's inside the exterior locking cap, then when I let off the nozzle, it would...disappear somewhere after a second or two. So, being hard-headed, I'd simply fill it again. This went on & on until I saw the dial and gave up.

There are no leaks anywhere on the bike. No drips or puddles on the garage or when riding.

So...where did it go? The garage WAS full of gas fumes this morning when I opened the door, but still no leaks or puddles.

UPDATE: OK. Something is up. The garage is filled with gas fumes so badly that they seep into the house during the night. Every morning I come downstairs to a strong gas smell, and have to crack the garage door right away. This whole thing was over a week ago, and I have burned thru 2 tanks by now (on both, I stopped well before the filler neck so it didn't happen again.)

Any idea what's going on? Is there something on this bike that fills with gas that I don't know about? Can't take much more.

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The stations meters is/or could be off.......... odd that it's in their favour....... :pissed:

Try a 5 gallon can (like for the mower), and see what happens.

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Check your oil level, on the odd chance that your floats in your carbs are set wrong/float needles are stuck you could be leaking fuel into the motor.

Gas evaporates pretty quickly especially in warm weather so you might have a slow leak that's hard to spot. Check all your fuel lines for rot.

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You might also want to check the rubber gasket that's on the gas cap itself. I had the same issue a few years ago, replaced the old gas cap, as the gasket was pretty stiff and dried out. The new gas cap sealed up just fine, and haven't really had the issue since.

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"come on baby light my fire".....

:tongue:

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What you are seeing and smelling is perfectly normal. I put excess of 5.8 gallons in my bike all the time when it has been on the fuel light for 15 miles or so. When you fill the tank to the very top air bleeds out of the portion of the tank that is above the lower lip of the filler neck, causing the level to go down. You can get an additional .6 gallons in this way but if you fill it this way just make sure you ride 5 miles or more before you park or as the fuel warms sitting in your garage it will expand and be vented out the tank overflow. There is nothing wrong with you bike at all.

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While I would really like to believe you, the "more than 5 miles before you park it" thing is throwing me off. Happened again last night. Fill up, kept it below the filler neck again, drove 40 miles home, and still had a garage full of fumes last night, and this morning too as I write this. I cracked open the cap multiple times last night (and earlier this week), even leaving it open once with no difference.

The garage isn't warm when I get home either. Sun is down, it's sheltered by a bunch of trees, etc. Over the weekend I left the door up all day too, so it wasn't warm in there.

The search continues....

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Have you taken the plastic off? It sounds like you may have a cracked fuel line somewhere.

and since I'm just throwing you-know-what against the wall, how does she start in the morning? A stuck carb float valve can get fairly smelly, too.

BTW, where in So Cal are you? I have very few answers, but sometimes a second pair of eyes helps.

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Are you sure it's your bike causing the smell? How about a leaking lawn mower or weed trimmer? I'd check the other gasoline powered equipment you have if you can't find anything with the bike.

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Are you sure it's your bike causing the smell? How about a leaking lawn mower or weed trimmer? I'd check the other gasoline powered equipment you have if you can't find anything with the bike.

HA! This is Southern CA! No one here does their own yardwork or owns that stuff!

(seriously the only things I have gas powered in the garage is the bikes...I don't know anyone that cuts their own grass, etc.)

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Have you taken the plastic off? It sounds like you may have a cracked fuel line somewhere.

and since I'm just throwing you-know-what against the wall, how does she start in the morning? A stuck carb float valve can get fairly smelly, too.

BTW, where in So Cal are you? I have very few answers, but sometimes a second pair of eyes helps.

I have not taken all the plastic off, but I did take off the tank (hoses still hooked up correctly and intact) and did not see/smell any leaks form the tank itself anywhere. As far as starting in the morning I will say that it used to start with one crank and go to fast idle right away on full choke, but lately it's been a crank 2 or 3 times and then it will run fine, but not as fast/high idle as before. If it does idle fast, it takes longer to get to high RPMs.

Had not thought about the stuck float. I suppose I can try a tap on the carbs, but that rarely works, I hear.

I'm in OC. If you're still in Ventura county, I'm a good long ways from you. Thanks for the thoughts though. I guess I'll tear it down again this weekend and double check it and try the tap on the carbs.

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Tore the bike down today, and it seems like I may have found the source of the gas smell. Took off the tank, flipped it over, and the insulation that's molded to the bottom of the tank was damp and had stain marks. Saw gas dribbling out (very little/very slowly) from where the fuel sending unit (that I installed a couple weeks ago due to the lo fuel light not working) connects to the tank. The O-ring is new as well, so I removed it, checked the o-ring, and put it back on. It really was maybe one or two drops a minute coming out from the bottom of the fuel sending unit base.

At least one of the bolts is stripped a little near the top of the bolt too. Anyone have any idea how to replace these? The bracket they are attached to seems welded to the bottom of the tank? Any ideas? Cannot tell for sure, but I think the bolts may be welded to the bracket as well, since they do not turn at all.

Right now, it is no longer leaking and the bolts are tight, but the bolts will have to be swapped if they have to come off again. This seems to be the issue, as I noticed I do not smell gas when the tank gets down to about half: which seems to be below the fuel sending unit base seal.

Did not see a canister on the bike at all, so now I know it's a non-CA version, BTW.

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Sounds like you are describing a welded stud that is stripped, not a bolt. Option 1: file it down and re-thread with a die the next step smaller. I don't know the mm size you are faced with as damaged, but even an SAE thread would be fine if it minimizes the amount you need to reduce the stud. Option 2: Pull the tank and flush it of all fuel traces and have a new stud welded in place of the bad one. Option3: check your smoke alarms and re-up the homeowner's insurance. :tongue: Anyone else?

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