Bike won't stay running below half tank

Maintenance, repair, troubleshooting, etc.
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cleight
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Mon Mar 24, 2014 8:13 am

Hello XJ experts,

I have a 94 XJ600 Seca II that I have been having trouble with for the past 2 seasons that I would like to get fixed before this season. Bike runs fairly good as long as it doesn't get below a half a tank. Once below a half tank the bike will dies and refuse to run doesn't matter if i change the petcock to reserve it will not start I am thinking it is fuel pump related but thought I would ask here before purchasing.

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1Oldman
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Mon Mar 24, 2014 9:55 am

Pop the cap and see if it's a venting issue. If that doesn't work, pull the petcock and check it out.
Better to be over the hill than under it.

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fateddy
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Mon Mar 24, 2014 10:31 am

Also check for vacuum leaks. Since both the petcock and fuel pump are vacuum-actuated, a vacuum leak could slow down flow pretty significantly.
Go soothingly on the grease mud, as there lurks the skid demon.

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cleight
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Mon Mar 24, 2014 11:05 am

I will try the gas cap venting to see if that helps, as it pertains to the Petcock a brand new one was installed about a year ago. I am not sure how the Vacuum host for the fuel pump should be connected as the bike has not had an intake box on it since I purchased it in 2009 previous owner removed it for some reason.

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cleight
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Mon Mar 24, 2014 12:56 pm

Is it possibly a bad fuel pump, i searched the forums but didn't find much pertaining to if the pumps are known for failing.

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Full Circle
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Mon Mar 24, 2014 2:03 pm

Is your new petcock a stock replacement? Is it vacuum actuated like the stock one? By intake box, do you mean the airbox?

Here's how to run all the lines...Fuel Lines

Here's what Casper called a Crude Fuel Pump Test

It might be your pump, they do fail but lets check everything suggested so far first. Could save you some coin.

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lucatnt
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Mon Mar 24, 2014 2:14 pm

I think from as describe him/it both a problem to the pomp in fact under half reservoir without the pomp cannot even reach gasoline the carburetors with the petcok in pri, check that there is no loss on the pipe depression of the pomp, in the worse one of the hypotheses would be able broken assere the menbrana of the pomp!

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radare
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Mon Mar 24, 2014 4:47 pm

I agree with lucatnt and others. Check your fuel pump for flow and ensure it has proper vacuum.

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Secarider4
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Tue Jun 06, 2017 8:50 pm

I am having this same problem currently. Any solution? I have recently rebuilt the petcock and have been riding on it for months with no issue. My fuel filter is also relatively new (2 yrs old). At half a tank my bike will die like it is out of gas. No flow will occur in the on or reserve petcock positions. The fuel filter is empty but is can see fuel in the line before and after the filter. Why is no flow occurring? If their is an issue with either my fuel pump or gas cap breather how can I test/remedy these problems?

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sleekitwan
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Tue Jun 06, 2017 11:53 pm

I throw in my cents -

We are all kind of assuming, when it is said dries up/engine dies after getting down to half a tank, you have been riding the bike sort of constantly, then it happens IE all in one ride. That, would be a build-up of something, like vacuum in tank, there's a little hole there in the cap mechanism, make sure it is clear. If however, you run it for a bit, it's fine, then more later, etc, and it is actually the fact the 'weight of fuel' is reduced to about half, that suggests fuel having trouble getting through.

So, check the little hole first in the cap area. Usually, it can be audible in hot weather, or cold weather with the cap closed, as changes are accommodated by it.

Second basic is the sound the fuel pump makes - here goes - prrk-k-k-k-k etc! A quite half-purr and half click sound in the bowels of the bike. this is the only time I am aware the pump is MEANT to run. It is primarily to prime-fill the float bowls after the bike's been sat. Put another way, I never hear it if I am starting up again after (yet another) pub lunch.

Third - fuel filter. Look, I never have a problem with these, but some people end up finding it's full of crud. Like with vacuum in tank, if you ride the bike hard, this should show up as killing the engine/power etc soon, perhaps in 15 minutes or half hour, as the fuel is removed sooner, or vacuum builds faster. In the short term, remove it to try or preferably, just have a two-buck filter bought and replace this - I use a see-through one for the obvious reason you can see the muck if it gathers.

Fourth - the petcock has 3 positions ( I know, it sounds patronising, but keep faith, be pedantic, and the problems will yield I promise). ON which is straight down on my XJ600N, PRI (prime) which is pointed to the back of the bike, then RES (reserve) which is that awful twiddly thing you gotta do once the engine becomes numbed and unresponsive on the highway just after you shook your fist at that group of Harley-Davidson ponces as you shot past. Anyway (touches bruises tenderly) that RES position is straight up.

My petcock gasket and seals are knackered, despite which I have no troubles, touch wood, because the float bowl sealing valve thingies must be in good shape. Your petcock as with the other person with the original fault on here, I note, had been refurbed with new gasket etc in the recent past. QUESTION: were the problems evident BEFORE and you changed the petcock gasket etc in order to try and resolve the issue, or there was no problem then you changed these parts, then problems developed apparently independently later? How many miles later?

The point of this is, was the bike laid up for a while before you got it? Any mileage check you can do or talk to the previous owner?

The common debris thing is, rust out of the tank, and other sediment. Now rust is clingy UNTIL it gets vibrated by the engine and road rumbles yes?! You see where I am going - if sat awhile, then you use the bike and it's an older bike, this rust is sprinkling off and dropping into the filter, and some will get past and sit in the float bowls - try undoing one of the little float bowl screws which brings me to the next point...

Five - if not DEBRIS, then what about WATER? Water has a nasty habit of sinking to the bottom of the tank. There, it sloshes around UNDER the 'gas' or petrol, because it has as many here know, a lower specific gravity IE it is less dense, not as heavy, as water. The little vertical tube with plastic gauze that forms an initial filter/reserve situation for the bike, and is attached to the petcock device, protruding into the tank, is I guess as easily 'blocked' from getting fuel into it, by lumps and grit, or water up to a 2" level. Put another way, if you had a boatload of water (2 inches) that would be above the level of this little plastic gauze tube, so no fuel would get in as it floats remember on top of the water.

It is possible, that a large weight of fuel, lots of it, while riding, on average as it were, slops around and sort of gets enough petrol to the engine to make it run, but during a ride, the water builds up in the float bowls and takes the place of fuel in there?

The check for water in the carb bowls, empty a float bowl or all of them maybe with the screw for this purpose. Any sign of water? Better, might be to take one bowl off entirely, not too hard, and you can LOOK and visibly see one liquid floating not mixing with the other?

It now should be apparent, that water sinking to the bottom of an uncoated tank, and rust appearing in a tank's insides on a sat bike, go together! There's always some air in a tank, always some water, and always some corrosive fuel. Were these bikes diesel, this problem would partly go away!

Hence, the standard and common experience, of draining all the fuel out into a safe container, removing the tank, getting ball bearings COUNT THEM and shaking it with a little fuel I suppose, to get the rust knocked off. Guys with expensive bikes and more money, get some coating then applied, not me though. Get most of that stuff out, add more fuel and slop it around (like a cup full) and repeat until it comes out clear.

The other issues are caused by user error like smearing grease on the float bowl edges, before refitting them. The grease goes rubbery or comes away in lumps, which block the carb jets just as good as debris, or better as it floats better. It looks jelly-like, like bad fuel. Again, laid-up bikes get varnish effect of old fuel that could float around and eventually help clog jets, etc.

That, is my starter list - if you re-open the petcock while you are there (emptying the tank is annoying, so you might well take a peek), you can double-check things look alright still - no weird bits floating around, no gasket wrongly placed? No grease turned to jelly blobs floating in there, imprisoned in the small cavities, an over-enthused amateur (me, a year ago) put there?

The last tip is that the two main routes for water to get into the fuel system, or carbs, are the air filter route, and the fuel tank route. Again, patronising but stick to the basics and the problems will succumb, step by step. I remember once, I set fire to the contents of the float bowl, and what was left, was water obviously, once the flames went out. You could empty it into another conteiner first I suppose - be careful with naked flames, there are probably less exciting ways to check for water in there.
Current bike year 2000 Yamaha XJ600N also called Seca II or Diversion 600. On an older bike air cooling is a blessing, no sludge and complexity of badly-maintained liquid cooling. Other bikes were: BMW K100 roadster; Honda VF750S Sabre with anti-dive.

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