intermittent loss of fuel

XXNUTZ

I don't know what is going on but my 98 has been displaying an intermittent loss of fuel to the carbs. It will start and run and warm up fine, then when I get on to go it runs out of fuel and dies. All of the lines are fine, if I lift the tank and set it back down, it starts right up and runs fine for a couple of days then does it again. It has died a couple of times while riding as well. The wierd thing is if I put it up on the center stand it will start and run. I'm thinking vacuum diaphram on the fuel tap. But why intermittent?? Any thoughts out there??

ironmike

It sounds like you're right - petcock diaphragm is the most likely suspect... and then miss-installed vacuum lines... it can give the same symptoms as vapor lock... Next time it happens, pop open your fuel tank - if you hear a whoosh of air rushing in... that pretty much confirms it.

Banshee

The other thing I can think of is some large particles of contamination in the fuel tank blocking the filter that feeds the tank valve. When you lift the tank it gets washed away from the gauze filter and you get fuel again, then over a period of time it gets sucked back by the fuel flow & blocks it again.

XXNUTZ

hello out there birdies, my suspicions were correct. It got warm enough to work on my 'bird and found that the diaphragm was split pretty good. I got a whole tap assembly from Honda and installed it. Now my next question is about the hoses that come off the bottom of the tank, one on each side of the tap assembly. I know that the larger of the two is an overflow that goes towards the ground. The smaller one I'm a bit confused about. When I bought the bike and it sat in the sun for a little bit, some fuel vapor and a bit of liquid would be coming out of this small hose. Normal?? I can kinda see the tube inside the tank and it goes from the bottom of the tank up to the filler cap area. On Honda's parts lookup, it looks like the vacuum line that goes to the tap diaphragm tee's off and goes to this tube on the bottom of the tank. If that's true, then wouldn't it run rich from the extra fuel vapor?? I need some advice from a fellow carbie rider about this hose routing. My Haynes XX manual is vague at best about the hose routing. they call it a breather hose. thanx for any and all advice.

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Banshee

Here you go! vacuum line

That thread has diagrams & explanations. Should answer your mystery line questions!

The leak would have been due to your split diaphragm. Long hose on left side of tank, overflow. Right side is tank breather (to T & 2 lines that go nowhere). 3rd line from #3, (on my '98), to the barb on the tap to open the diaphragm operated tap. If the diaphragm is intact, no fuel or vapour will go through to the manifold.

wwmiv

I just got back from a 12 day ride out to Wyoming. The only problem I had was this: At about 1/4 tank, after running highway speeds between 70 and 90 mph (starting with a full tank), I would get symptoms of running out of fuel. This only occurred when I was at 1/4 tank or lower. In the most extreme case, I did have to pull over, stop the engine, open the gas tank, close it, and then be on my way. I did not hear a vacuum sound when opening up the gas cap. Does this also sound like a vacuum tube issue or ???? Anyone else have symptoms like this? Again, I never had a problem except after being out on the road running a full tank down to 1/4 tank.

XXNUTZ

I had the split diaphragm on mine and it would act up no matter how much fuel I had in the tank. Since replacing the tap assembly, no problems since. Cheers.

wwmiv

Thanks, I'll look that up in the manual.

XXNUTZ

I believe that there is a rebuild kit available for the tap, I replaced the whole assembly at a much greater cost. Check with your local Honda dealer for the kit. There is a downloadable service manual on this site to help you out as well. Hope this helps, Cheers.