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Over flow & potential fuel leak 98 VTR

Old 12-19-2015, 01:07 PM
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Over flow & potential fuel leak 98 VTR

I just purchased a 98 VTR 1000 last week. Fun bike!

It had 1/2 tank of gas when I picked it up....I filled it up after trip meter said 125 miles.
Got home and noticed gas smell. Next morning I noticed gas residue on left side of frame....nothing on the floor though.
I installed a set of Two Bro.s pipes & went for a test ride...very nice and throaty!!
Got about 2 miles out and the gas light came on...only 19 miles!!
Filled up and came home ....fuel constantly dripping out the overflow ?
Still nothing on the floor.
Any thoughts would be appreciated!!
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Old 12-19-2015, 03:37 PM
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Split fuel pipe / Split petcock vacuum diaphragm? Take tank off and see where the problem is.
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Old 12-19-2015, 03:44 PM
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Light A Torch To See

When you say "overflow" do you mean the 6mm ID hose from the bottom right rear of the fuel tank that should run down and to the left and exit behind and below the left rear of the chin fairing?

Be sure the vacuum hose from rear carb intake manifold that opens the fuel petcock is connected to the left side of the petcock and not its bottom spigot (which is its drain port).

Also be sure the 3mm ID hose from the fuel tank internal vent pipe (which is the smaller spigot adjacent the filler opening overflow outlet pipe under the tank) is not kinked and I run mine down on the left side behind the the clutch slave. I also have a T-fitting in the hose under the tank that has a L-shaped hose that connects to a fuel tank check-valve vent.

But it could be the petcock itself leaking between where it fits up into the fuel tank (unlikely) past the O-ring and secured with 2 screws (that could have loosed, again unlikely), or where its 2 halves vertically clamp together whose mating surfaces are sealed with the vacuum actuated diaphragm that contains a little nub that plugs fuel flow, and/or and most likely the diaphragm tore or has a pin-hole and fuel is leaking past it out the bottom drain spigot.

However, if one or both (probably rear) carb fuel valves that is actuated by the fuel float is stuck open by a piece of dried fuel shellac or "crap", the float is fuel-logged (will not float and close the fuel valve), or the fuel valve needle or seat are worn, gas will overflow between the cylinders and leak down the left side when on the side stand.

Yes, it could also be a leaking fuel line hose at a carb or petcock...

Light a torch and look around carefully under the fuel tank LOL!

Originally Posted by 118811 View Post
I just purchased a 98 VTR 1000 last week. Fun bike!

It had 1/2 tank of gas when I picked it up....I filled it up after trip meter said 125 miles.
Got home and noticed gas smell. Next morning I noticed gas residue on left side of frame....nothing on the floor though.
I installed a set of Two Bro.s pipes & went for a test ride...very nice and throaty!!
Got about 2 miles out and the gas light came on...only 19 miles!!
Filled up and came home ....fuel constantly dripping out the overflow ?
Still nothing on the floor.
Any thoughts would be appreciated!!
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Old 12-19-2015, 06:08 PM
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When I say overflow.....I'm talking about an outlet at the rear of tank, it's visible in the gap between seat and tank.
Gas jus constantly burps out of it.
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Old 12-19-2015, 09:07 PM
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Originally Posted by 118811 View Post
When I say overflow.....I'm talking about an outlet at the rear of tank, it's visible in the gap between seat and tank.
Gas jus constantly burps out of it.
If you read my reply that overflow outlet should have a hose on it that runs down to the left all the way to the front to the left rear of the chin fairing you may be over filling the tank there's a fill bar across the filler opening you shouldn't fill it much above

However I fill to the brim and don't have problems
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Old 12-20-2015, 09:50 AM
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Pictures speak a thousand words.

Overflows are mid tank on the bottom. Petcock is at the rear. You wouldn't notice when the bike is off outside a few drops but when the bike is running it will pour out of the petcock. Sounds like you have a loose or bad hose.

Pull the front 2 screws on the tank and the underside bolt to remove the tank and reattach / replace the hose. Reattach the tank and ride on.
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Old 12-20-2015, 11:12 AM
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Thanks again for the reply's...all!

It's been pouring the last few days here in Honolulu...so I haven't had a chance to check out my issue.

I do hope it's just a bad or loose/unconnected fuel line!!

It just reeks of gas under the cover....I agree Meier, it has to be more than just over flow.
Though I do think I over filled the tank.

I hope to post up good news soon.

I really do like this bike! I had a highly modified 98' Ducati M900 Monster....which suffered a slow death. This bike with the new exhaust brings back those V Twin good memories!!
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Old 12-20-2015, 11:25 AM
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While the bike is running on side stand ....should I see gas draining out, if it is a bad hose?
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Old 12-20-2015, 12:29 PM
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The VTR has a vacuum diaphragm valve which should shut off fuel when to the carbs when the motor is off. These do give problems with age, the diaphragm can perish and leak fuel through to the drain (and maybe this is your specific problem), they can also stick open so fuel will flow to the carbs when the motor is off and potentially overflow them (this also requires poor float valves in the carbs).

From the petcock, you should have two large hoses running to the carbs, and one smaller hose which attaches to the inlet of the rear cylinder and is the vacuum line.

The fuel tank will have two hoses, an air vent which terminates inside at the top of the tank, and also the gas cap overflow for when you are clumsy filling the tank. Under normal operation fuel should not be coming out of either.

As a first step I'd suggest pulling the tank off the bike and dismantling the petcock. Lift the front of the tank and prop it up, turn the manual tap fully clockwise to shut the valve, remove the hoses (a small spillage will happen from the fuel-to-carb pipes), disconnect the low-fuel sensor connector at the back of the tank and then take the tank off the bike. Easier to do this with a mostly empty tank. Flip the tank upside down (the cap will seal) and rest it on something soft and you can then remove the petcock for some examination. From memory there are two bolts holding the petcock to the tank, remove these and the petcock and fuel strainer will pull out of the tank (watch for the sealing o-ring). Now is a good opportunity to clean the strainer if needed.

With the manual tap opened (fully counterclockwise) you should be able to test the vacuum petcock by sucking on the vacuum fitting (I use my vacuum brake bleeder for this) and then seeing if liquid will flow from the tank side through the petcock. With the vacuum released, nothing should flow. If you can't get a vacuum to hold then the diaphragm is toast. If the valve sticks open when the vacuum is released, the diaphragm should be replaced as well.

I used this part number for the replacement; a generic Honda petcock part:

16953-ML0-034 COVER SET, PETCOCK $31.53

Good luck and let us know what you find.
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Old 12-20-2015, 01:04 PM
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Cadbury,
Thank you so much for such a complete & detailed plan of action!!
I will attempt your plan Monday or Tuesday weather permitting.
Might have to ride around the neighborhood to burn off some gas since I just filled up.
I'm not the most mechanically inclined....so wish me luck!!
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Old 12-20-2015, 02:07 PM
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Do I potentially need the above cover kit or this membrane kit?

1997 2005 Honda Superhawk VTR1000F VTR1000 K L Fuel Petcock Repair Kit 18 5015 | eBay

Last edited by 118811; 12-20-2015 at 03:57 PM.
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Old 12-20-2015, 05:11 PM
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I covered all the same things, though I did not mention the strainer above the petcock in the tank.

If you draw to hard with a vacuum pump, you will destroy the diaphragm.

If the carb hoses to the petcock are not the issue, the petcock is most likely but the carb floats and/or float valves could cause the cylinders to fill with fuel which if started could bend a connecting rod.

If you are not mechanically inclined, find someone who is you trust. The shop manual covers all this.

Testing the petcock on the tank is easy though, it does not need to be removed to test it.

No more spoon feeding.
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Old 12-20-2015, 06:20 PM
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Originally Posted by 118811 View Post
Do I potentially need the above cover kit or this membrane kit?

1997 2005 Honda Superhawk VTR1000F VTR1000 K L Fuel Petcock Repair Kit 18 5015 | eBay
The genuine Honda parts has all that and more, and is cheaper. Your call

Not sure how you'd destroy a vacuum diaphragm by drawing a vacuum on it?
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Old 12-20-2015, 06:28 PM
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Originally Posted by Cadbury64 View Post
Not sure how you'd destroy a vacuum diaphragm by drawing a vacuum on it?
A MityVac or similar vacuum pump can draw down to -28 psi easy. The petcock is design operate at only -2 or 3 psi, and the diaphragm can tear easily.
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Old 12-20-2015, 08:41 PM
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How much you fill the tank can cause issues with vapor lock. Not over flow to knock you down to 19 miles on the tank. That's not how the over flow works.

If the tank is full then pull the petcock lines into the carbs and drain the full tank into a clean bucket so you can reuse the fuel. You will have to pull the carb vac line from the rear carb and literally suck on it to open the diaphram to let the fuel flow.

I'm thinking this a line issue and not a diaphram issue.

The bike will get more then that distance on a blown diaphram. I got 15 miles to the gallon with a huge hole in the petcock diaphrams.

Facts stated: bike runs. No fuel leaking when the bike is off. Looses fuel when the bike is running. Over fill won't affect the applied mileage per gallon to the point where you get less then 100+ miles to a tank.

I'm drunk but simply put drain the tank and check the lines. If you are leaking out if the left side rear it can't be anything other then that.

I ask again for pictures.
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Old 12-21-2015, 11:53 AM
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Originally Posted by skokievtr View Post
A MityVac or similar vacuum pump can draw down to -28 psi easy. The petcock is design operate at only -2 or 3 psi, and the diaphragm can tear easily.
The maximum vacuum that you can draw with any device is 1 atmosphere or about 14psi. Given the diaphragm pulls up against the shell and there is just a tiny pinhole for the vacuum to draw through, I highly doubt you'd ever be able to damage the diaphragm by sucking on it.

With my health and safety hat on, I'd rather advise someone to use a vacuum pump to draw on a potentially fuel-filled hose than their mouth!
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Old 12-21-2015, 02:09 PM
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I used a small vacuum pump when I function tested the valve on my bike with the tank off. The petcock worked perfectly when I turned the pump on, then off.
Out of curiosity, I tried the mouth method. Much to my surprise, it took very little effort to cycle the valve on.
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Old 12-22-2015, 11:35 AM
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Thanks again for all of the replies!

I have leak for sure. Finally was able to lift the tank up....nothing appeared out of place, broken or torn.
Started the bike and it ran fine.....gas light came on!!!
This tank I got less than 1 mile. ;-)

I was able to ride to the shop which is only 2/3rds of a mile away.
I now await the mechanics call.
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Old 12-22-2015, 02:16 PM
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Mechanic just called to inform me that I in fact have a blown diaphram in the petcock.
Local Honda dealer doesn't have part... :-(
So I ordered parts from Partzilla...I should be riding by We'd. Next week.

Thank to all of you for your advice.
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