Carb is draining... and draining... and draining....

adouglas · October 11th, 2009, 03:09 PM

Riddle me this, Batman...

I put my bike away for the winter today. After filling the tank to the brim with stabilized fuel and changing the oil, I went to drain the carbs.

Those float bowls aren't that big, so I just stuffed a big wad of paper towels in there to soak up the few ounces of fuel that ought to come out. Well, the towels saturated, so I shut the tap off.

Hm. More than I thought.

I hunted around in the garage and found an 18-inch long piece of clear plastic tubing about 1/2" in diameter with a cap on one end. Way too big to fit snugly on the float bowl nipple, but it served well to catch fuel.

So I opened the tap and filled my catch tube, which holds maybe a couple of ounces or so. I popped the gas cap open and poured the fuel back in the tank. I repeated this procedure.

Six, seven, maybe eight times. Gas continued to flow. I didn't measure, but I must have drained 10 to 12 ounces out of one carb, and there was no end in sight. At that point I figured I'd better just stop and button the bike up before the sun went down. Worst case is that I store it with stabilized fuel in the carbs.

WTF? The bike runs flawlessly, so I don't think there's anything wrong. I checked the main valve and it is switched to ON, not PRI.

The only thing I can figure that could cause this is a double failure... faulty petcock AND faulty float valve in the carb. But not only is that very unlikely, wouldn't it cause some other symptom?

Anyone got any ideas here?

g21-30 · October 11th, 2009, 03:15 PM

If the valve is not on PRI, gas is only "supposed" to flow when there is a vacuum present. Disconnect the vacuum line from the valve and try it again.

adouglas · October 11th, 2009, 04:35 PM

Quote:

Originally Posted by g21-30

If the valve is not on PRI, gas is only "supposed" to flow when there is a vacuum present. Disconnect the vacuum line from the valve and try it again.

Wait a minute... isn't the vacuum at the petcock caused by engine operation? Are you suggesting that there is vacuum in that line after the engine stops?

If there isn't vacuum in that line (don't see how there could be), if I simply disconnect the vacuum line, how will that change anything?

At this point I'm not going to have any opportunity to work on the bike at all for two weeks, and even then it'll be a challenge to find the time. Chances are it'll have to stay as it is until spring.

I'd still like to find out what's going on, though.

g21-30 · October 11th, 2009, 05:27 PM

That's my point! Disconnect the vacuum line and you will know for sure there isn't a vacuum present. If you search, you will see that at least one person has had a failed valve, i.e. gas flowed without a vacuum present and the valve NOT set to PRI! Bottom line....you may have discovered that you have a bad valve.

You might do as Sailariel does and pinch shut the fuel line leading into the valve, prior to draining the bowls!

HKr1 · October 11th, 2009, 05:29 PM

I wouldnt store any carb empty, Unless its bran new in the box. Why dont you just put in the stabil, give her a good baby shaking(mixing it a bit), and run the motor for a few. < So that mix is in the carbs.

backinthesaddleagain · October 11th, 2009, 05:42 PM

Andrew - 2 good fall new england days this weekend for riding. Sure you want to shut her down already? I

adouglas · October 11th, 2009, 06:36 PM

Can't do the storage thing during the week, and can't deal with the bike at all next weekend... my band has a gig Saturday (if you're anywhere near southwestern CT come see us! The Lumberyard in Georgetown, just off US 7), then Sunday I have to hit the road for Missouri.

Anyway, I did some more thinking. My earlier thought about a double failure was based on backwards thinking... the float valve shuts when the bowl is full, so it makes sense that it'd just flow as long as the supply is there.

The obvious answer is a faulty petcock. If the petcock were not faulty there would have to somehow be a vacuum held on it without the bike running... and I don't see how that could happen.

So... what symptoms are there if you've got a faulty petcock? Shouldn't it manifest itself in some way in normal operation?

adouglas · October 11th, 2009, 06:38 PM

Quote:

Originally Posted by HKr1

I wouldnt store any carb empty, Unless its bran new in the box. Why dont you just put in the stabil, give her a good baby shaking(mixing it a bit), and run the motor for a few. < So that mix is in the carbs.

I just stabilized the last tank as well as the storage tank. That way the whole system definitely has marine stabil-treated fuel in it.

g21-30 · October 12th, 2009, 07:13 AM

Quote:

Originally Posted by adouglas

So... what symptoms are there if you've got a faulty petcock? Shouldn't it manifest itself in some way in normal operation?

Normal operation...vacuum (ON position) opens the valve (petcock). If the valve is faulty and stays open (possibly your problem) when no vacuum is present, you still have normal operation, i.e. the engine starts and runs!

If you have the valve set in the PRI position and drain the bowls, then you will have gas flowing until the TANK is drained! Is this perhaps your problem?

adouglas · October 12th, 2009, 08:08 AM

Nope. Definitely set to ON, not PRI.

I've read somewhere about fuel overflowing and dripping out of the carbs if the vacuum valve is faulty. Is this correct?

If not, and the bike operates perfectly normally with a bad vacuum valve -- no adverse effect other than the inability to easily take the tank off and drain the carbs -- then why the heck is there a vacuum valve in the first place? A simple ON-OFF petcock would be cheaper, simpler and more reliable!

g21-30 · October 12th, 2009, 08:52 AM

The float needle-valve controls the flow of fuel into the bowl.

adouglas · October 12th, 2009, 10:11 AM

Yeah... so zero symptoms other than the inability to drain the carbs without also draining the tank? Is that correct?

Fortunately rebuild of the petcock appears to be fairly simple and straightforward if it turns out to be needed. Just a few gaskets and an o-ring. But there is that whole tank-draining hassle, plus concern over introducing leaks.

g21-30 · October 29th, 2009, 04:43 PM

Any update?

adouglas · October 29th, 2009, 08:25 PM

No, I just decided to leave the carbs as they are, with stabilized gas in them. The bike has been put up for the winter.

October 11th, 2009, 03:09 PM	#1
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Carb is draining... and draining... and draining.... Riddle me this, Batman... I put my bike away for the winter today. After filling the tank to the brim with stabilized fuel and changing the oil, I went to drain the carbs. Those float bowls aren't that big, so I just stuffed a big wad of paper towels in there to soak up the few ounces of fuel that ought to come out. Well, the towels saturated, so I shut the tap off. Hm. More than I thought. I hunted around in the garage and found an 18-inch long piece of clear plastic tubing about 1/2" in diameter with a cap on one end. Way too big to fit snugly on the float bowl nipple, but it served well to catch fuel. So I opened the tap and filled my catch tube, which holds maybe a couple of ounces or so. I popped the gas cap open and poured the fuel back in the tank. I repeated this procedure. Six, seven, maybe eight times. Gas continued to flow. I didn't measure, but I must have drained 10 to 12 ounces out of one carb, and there was no end in sight. At that point I figured I'd better just stop and button the bike up before the sun went down. Worst case is that I store it with stabilized fuel in the carbs. WTF? The bike runs flawlessly, so I don't think there's anything wrong. I checked the main valve and it is switched to ON, not PRI. The only thing I can figure that could cause this is a double failure... faulty petcock AND faulty float valve in the carb. But not only is that very unlikely, wouldn't it cause some other symptom? Anyone got any ideas here?

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October 11th, 2009, 03:15 PM	#2
g21-30 ninjette.org certified postwhore Name: Sam Location: Northern Virginia Join Date: Nov 2008 Motorcycle(s): Ninja 250R 2009 and ZX-12R 2000 Posts: A lot.	If the valve is not on PRI, gas is only "supposed" to flow when there is a vacuum present. Disconnect the vacuum line from the valve and try it again.

October 11th, 2009, 05:27 PM	#4
g21-30 ninjette.org certified postwhore Name: Sam Location: Northern Virginia Join Date: Nov 2008 Motorcycle(s): Ninja 250R 2009 and ZX-12R 2000 Posts: A lot.	That's my point! Disconnect the vacuum line and you will know for sure there isn't a vacuum present. If you search, you will see that at least one person has had a failed valve, i.e. gas flowed without a vacuum present and the valve NOT set to PRI! Bottom line....you may have discovered that you have a bad valve. You might do as Sailariel does and pinch shut the fuel line leading into the valve, prior to draining the bowls!

October 11th, 2009, 05:29 PM	#5
HKr1 IC2(SW) Name: Kerry Location: Pensacola Join Date: Nov 2008 Motorcycle(s): . Posts: A lot.	I wouldnt store any carb empty, Unless its bran new in the box. Why dont you just put in the stabil, give her a good baby shaking(mixing it a bit), and run the motor for a few. < So that mix is in the carbs.

October 11th, 2009, 05:42 PM	#6
backinthesaddleagain ninjette.org certified postwhore Name: Greg Location: Rhode Island Join Date: Apr 2009 Motorcycle(s): 2013 ZX6R 636 Posts: A lot.	Andrew - 2 good fall new england days this weekend for riding. Sure you want to shut her down already? I

October 11th, 2009, 06:36 PM	#7
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Can't do the storage thing during the week, and can't deal with the bike at all next weekend... my band has a gig Saturday (if you're anywhere near southwestern CT come see us! The Lumberyard in Georgetown, just off US 7), then Sunday I have to hit the road for Missouri. Anyway, I did some more thinking. My earlier thought about a double failure was based on backwards thinking... the float valve shuts when the bowl is full, so it makes sense that it'd just flow as long as the supply is there. The obvious answer is a faulty petcock. If the petcock were not faulty there would have to somehow be a vacuum held on it without the bike running... and I don't see how that could happen. So... what symptoms are there if you've got a faulty petcock? Shouldn't it manifest itself in some way in normal operation?

October 12th, 2009, 08:08 AM	#10
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Nope. Definitely set to ON, not PRI. I've read somewhere about fuel overflowing and dripping out of the carbs if the vacuum valve is faulty. Is this correct? If not, and the bike operates perfectly normally with a bad vacuum valve -- no adverse effect other than the inability to easily take the tank off and drain the carbs -- then why the heck is there a vacuum valve in the first place? A simple ON-OFF petcock would be cheaper, simpler and more reliable!

October 12th, 2009, 08:52 AM	#11
g21-30 ninjette.org certified postwhore Name: Sam Location: Northern Virginia Join Date: Nov 2008 Motorcycle(s): Ninja 250R 2009 and ZX-12R 2000 Posts: A lot.	The float needle-valve controls the flow of fuel into the bowl.

October 12th, 2009, 10:11 AM	#12
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	Yeah... so zero symptoms other than the inability to drain the carbs without also draining the tank? Is that correct? Fortunately rebuild of the petcock appears to be fairly simple and straightforward if it turns out to be needed. Just a few gaskets and an o-ring. But there is that whole tank-draining hassle, plus concern over introducing leaks.

October 29th, 2009, 04:43 PM	#13
g21-30 ninjette.org certified postwhore Name: Sam Location: Northern Virginia Join Date: Nov 2008 Motorcycle(s): Ninja 250R 2009 and ZX-12R 2000 Posts: A lot.	Any update?

October 29th, 2009, 08:25 PM	#14
adouglas Cat herder Name: Gort Location: A secret lair which, being secret, has an undisclosed location Join Date: May 2009 Motorcycle(s): Aprilia RS660 Posts: A lot. Blog Entries: 6 MOTM - Jul '18, Nov '16, Aug '14, May '13	No, I just decided to leave the carbs as they are, with stabilized gas in them. The bike has been put up for the winter.