Author Topic: Leaking carbs... or petcock... or?  (Read 254 times)

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Offline tbharker

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Leaking carbs... or petcock... or?
« on: June 04, 2018, 10:31:42 pm »
I've owned this '86 Connie for 7 years. Every year, after winter, the carbs are gummed up, so this past winter I drained the carbs (what a nightmare).

Long story short, I filled up the tank this spring, and fuel started flowing out the tops of all four carbs, but only in the PRI position. When I turn it to ON, the flow stops. Bike runs GREAT (so carb drain did it's thing).

I can run it in the ON position, no problem. I'm just wondering why the PRI position causes it to overflow, or if that's just normal if I leave it in the PRI position for too long.

[Other notes: nothing is connected to the second, smaller, brass nipple on the petcock. Am I missing a hose? Also, I'm not entirely confident I have the hoses connected to the correct ports on the low end of the tank...]

Offline Mettler1

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Re: Leaking carbs... or petcock... or?
« Reply #1 on: June 04, 2018, 11:08:59 pm »
  Do not try to start the engine UNTIL the fuel problem is fix!! Fuel should NOT ever leak out of the carbs UNLESS they have a real problem. Read about HYDROLOCK!! and what it can do to your engine!!  :o :o  You should be able to turn your petcock on and not have any fuel leaking from the carbs!! Sounds like something very wrong with your fuel system!!


  Do some reading and watch some videos about HYDROLOCK!!


                 https://sites.google.com/site/shoodabenengineering/
'94 Concours 115,000 miles-- 7th gear,2MM,KB fork brace,Over flowtubes,Stick coils,Tcro shifter,GPS,SiSF'sTorque cams,SPOOKFAK,block off plates, SS brake & clutch lines,KB risers, FENDA EXTENDA, emulators, SiSF carb Spa, Delkevic exhaust, Murphs' knee savers +grips, etc

Offline DC Concours

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Re: Leaking carbs... or petcock... or?
« Reply #2 on: June 04, 2018, 11:18:18 pm »
How does it run on the on setting if the vacuum line is not connected? How have you not had a hydrolock yet?

You need to rehook the vacuum line check or replace the petcock and your carbs need a full overhaul.

Offline Stasch

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Re: Leaking carbs... or petcock... or?
« Reply #3 on: June 05, 2018, 01:08:53 am »
Quote
fuel started flowing out the tops of all four carbs, but only in the PRI position. When I turn it to ON, the flow stops. Bike runs GREAT (so carb drain did it's thing).

DC Concours is asking some good questions.

Your post is a bit confusing.  Not trying to bust your chops, but to get better info.  The fuel cannot come out of the tops of the carbs unless . . .  possibly . . . . you have somehow connected the fuel line to one of the carb vent tubes?

If the vacuum line isn't connected you will run the carb bowls dry.

Quote
so carb drain did it's thing

Does this mean you have overflow tubes in your carb bowls?

Kinda need to sort this and your connections out before you start thinking about rebuilding stuff.

(edited for spelling and grammer)
« Last Edit: June 05, 2018, 03:25:39 pm by Stasch »
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Offline tbharker

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Re: Leaking carbs... or petcock... or?
« Reply #4 on: June 05, 2018, 02:46:57 pm »
  Do not try to start the engine UNTIL the fuel problem is fix!! Fuel should NOT ever leak out of the carbs UNLESS they have a real problem. Read about HYDROLOCK!! and what it can do to your engine!!  :o :o  You should be able to turn your petcock on and not have any fuel leaking from the carbs!! Sounds like something very wrong with your fuel system!!


  Do some reading and watch some videos about HYDROLOCK!!


                 https://sites.google.com/site/shoodabenengineering/

Solid advice. Trust me, I've read up on hydrolock--I don't think you can read through this forum (or any forum related to the Connie, for that matter) without the discussion turning to the dreaded hydrolock! For the time being, I'm not hydrolocked, but the more I read, the more I'm convinced my Connie will inevitably die of hydrolock.  ;)

Offline DC Concours

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Re: Leaking carbs... or petcock... or?
« Reply #5 on: June 05, 2018, 02:54:40 pm »
How many miles on your bike and when were the carbs last serviced? Yours is an old bike so carbs definitely need servicing if not serviced before. also consider changing the petcock and get the over flow tubes.

Offline tbharker

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Re: Leaking carbs... or petcock... or?
« Reply #6 on: June 05, 2018, 03:37:36 pm »
How many miles on your bike and when were the carbs last serviced? Yours is an old bike so carbs definitely need servicing if not serviced before. also consider changing the petcock and get the over flow tubes.

Bike has about 60k miles on it, I've had the carbs professionally serviced almost every year, including last year, because they got gummed up over the winter. The carbs seem solid still (a new servicing seems overkill, unless there's a fear something 'dried up' over the winter). It doesn't seem to me that's the issue.

I just put a brand new OEM petcock on the bike a year or so ago. I could do ALL the recommended upgrades, but at this point, I'm just trying to get her running before the summer is over.  :)

Offline tbharker

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Re: Leaking carbs... or petcock... or?
« Reply #7 on: June 05, 2018, 03:38:47 pm »
Quote
DC Concours is asking some good questions.

Your post is a bit confusing.  Not trying to bust your chops, but to get better info.  The fuel cannot come out of the tops of the carbs unless . . .  possibly . . . . you have somehow connected the fuel line to one of the a carb vent tube?

Okay, I don't have the fuel line connected to a carb vent tube--it's just connected to the same fuel line it's always been connected to. That said, the major question mark is the missing vacuum line--maybe that's allowing the carbs to fill up and seep out somewhere? Admittedly, I don't know carbs well enough to make an educated guess. Further, I don't know exactly where it's coming out of the carbs, only that it's not the drains on the bottom, but rather from up above where I can visually see (and all four start overflowing at the same time).

Quote
If the vacuum line isn't connected you will run the carb bowls dry.

Okay, so I ran it for a few minutes today and it ended up stalling out after a minute or two. So I think you're right--the bowls have run dry, and it was just running on whatever fuel was left in the carb bowls from when I had it on PRIme.

Quote
Does this mean you have overflow tubes in your carb bowls?

To be completely honest, I have no idea if I have overflow tubes or not. The guy I bought it from had done quite a bit of customization (most of it not great), so I'm constantly finding new things I need to undo and/or redo.

(1) Is there a diagram somewhere of how the fuel hoses should all hook up? I've searched a few times, but haven't found anything definitive. Clearly I've screwed up the hookups, and it's been so long since I took everything apart, I can't remember. I thought I'd labeled the hoses to protect myself from memory failure, but I must have gotten fuel on the tags, so the ink disappeared... 
(2) I've got three nipples on the low end of my tank, and three hose ends--should one of those be connecting to the vacuum line, or a fourth (if I connect the nipple on petcock for the vaccuum line to a hose, where does the other end go?)? I've read that at least a couple of these nipples have something to do with California smog, or something, but I only know enough to screw something up.
(3) two of the hoses are clear (or were, back in 1986), and the third is black and just seems to be some kind of vent or drain, hanging down in the the middle of the bike. The hoses are pretty hard--can I just replace them with standard automotive fuel line, or do I need to find some transparent hose somewhere?

I'm not really sure how to upload pictures to this forum, so here are a couple dropbox links to images, if it's any help:
https://www.dropbox.com/s/s0lg1nlsiig40yi/COG_TANK.jpg?dl=0
https://www.dropbox.com/s/lzvec2fkwi1mgkk/COG_VENT.jpg?dl=0
https://www.dropbox.com/s/9kp62wu5t1c7kke/COG_PETCOCK-carbs.jpg?dl=0

Offline Stasch

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Re: Leaking carbs... or petcock... or?
« Reply #8 on: June 05, 2018, 05:22:48 pm »
Quote
Is there a diagram somewhere of how the fuel hoses should all hook up

Yes, a Clymer or factory service manual will have this info.

There are 2 barbs coming out of the petcock.  A fat one towards the outside (the fuel line) and a smaller one to the inside (the vacuum line)

The fuel line connects to a 'T' connection between carbs 2 and 3 down near the bottom  (count the cylinders / carbs from left to right while seated, 1 through 4, starting with 1 on your left).

The vacuum line needs to connect from the smaller petcock barb to the number 2 carb's vacuum port found at the front of the carbs just before the rubber manifold that connects to the cylinder head.   Carb 1 and 4 vacuum ports are connected to the breather / reed valves on the cylinder cover when OEM, many remove the breather reeds in which case 1 and 4 need to be capped.  Carb 3 vacuum port is plugged when OEM, but is often used to feed an after market cruise control.

If you have an OEM petcock, which it sounds like you do,  there is no 'OFF'.  PRIME is a free flow gravity feed used to prime empty carb bowls or when the fuel in those carb bowls has evaporated due to storage.  'ON' and 'RES' only allow fuel to flow when the vacuum from the carbs holds a diaphram open to allow fuel flow.  The concept is the fuel only flows when the bike is running - no need for manual ON or OFF as the lack of vacuum is supposed to allow a spring to close the diaphram to turn the flow OFF. 

The BIG IF is if petcock is leaking down into the carb bowls even when there's no vacuum.  That is where overflow tubes come in, (not OEM) allowing access fuel to flow out of the tubes onto the ground, rather than to back up into the airbox or worse, into a cylinder(s) that may have partially open intake valves - leading to potential for the big H - hydrolock.
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Offline Stasch

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Re: Leaking carbs... or petcock... or?
« Reply #9 on: June 05, 2018, 05:29:52 pm »
Quote
To be completely honest, I have no idea if I have overflow tubes or not. The guy I bought it from had done quite a bit of customization (most of it not great), so I'm constantly finding new things I need to undo and/or redo.

This is easy to determine.  You need a ~1/8" tube to attach over one of the nip-ples.  Gently blow some air through it.

If air passes through, you have overflow tubes.  If air doesn't flow - you don't have 'em.

I can't speak exactly to the 3 tubes at the rear of the tank as that sounds like a Cali model, so read the following with that in mind.

On the 2 hose non-Cali models, one is an air vent, the other is an overflow tube for fuel that gets sloshed or spilled in the filler cap hole when fueling.  Both route to the bottom of the frame next to the where the battery vent hose exhausts.

The 3rd Cali hose MAY go to the charcoal canister if it still exists on the bike.  Others will have to chime in here.  A service manual will cover all of this too.
« Last Edit: June 05, 2018, 05:48:41 pm by Stasch »
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Offline Stasch

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Re: Leaking carbs... or petcock... or?
« Reply #10 on: June 05, 2018, 05:42:21 pm »
In your 3rd pic, you can see the number 1 carb's vacuum port with a hose on it - looks like it is an OEM connection to the reed valve connection from ports 1 and 4 to the cylinder head. 

The other vacuum ports are in the same position on carbs 2 through 4.

If you are missing the vacuum line connection to the petcock it will not allow fuel flow UNLESS its defective, and then probably not in an amount sufficient to keep the bike running for long. 

You need to find out where the fuel is leaking out of the carbs when PRIME is on.  If that doesn't get fixed, the same thing will likely happen once the vacuum line is properly installed and the bike is running.

Is the fuel line properly connected to the 'T' between carb bowl's 2 and 3?  Is it leaking there?

There are additional fuel tubes connecting carbs 1 and 2, then 3 and 4 near the bottom of the carb bodies so fuel can get to all the carbs - could be leaking there.

While odd that all 4 began leaking simultaneously, its possible some type of carb cleaner was used that degraded the rubber for the orings that seal the fuel feed tubes, orings sealing the carb bowls, the rubber tips of the float valve, etc.

I would want to know where the problem spots are before I took it all apart, even if you plan to send the carbs off for a rework.  (I highly recommend SISF for this)  It could be from a loose connection or other source.
« Last Edit: June 05, 2018, 05:47:26 pm by Stasch »
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He IS a racer, hence the forward lean!!  by: Mettler1