Fuel drip problems - on the right track?

[Pearson]

Hi all. I've been lurking since buying a 1978 GS750 just over a month ago. Been using the forum alot to help me get through a host of problems and like all others, find the info. invaluable.

I'm really making good progress on the bike. It wasn't running, then was running rough and now is getting pretty close. With just a bench sync, 2 of 3 plugs are a nice color and I'm closing in on the the last 2 two plugs on carbs 1 & 2. I will wrench on most anything, though I have no experience. I've taken the carbs apart and cleaned everything but the pilot jet since that one was painted in.

I'd like to bounce my thoughts off you all and see if I"m heading in the right direction:
1. I'm getting way too much fuel delivered. After going for a brief ride, No.2 carb drips at a rate of 1/sec. on the side stand and dumps a solid squirt of gas when on the center. I've ridden the bike and tested the petcock in all positions and found that on PRI I'll flood the bike out and get alot of gas dripping from No.2. While in the ON position, the bike will starve and die. While in RES, the bike runs great though No.2 will still drip. I think I need to rebuild the existing petcock or go to the pingel??

2. Next I'm confused if the petcock is responsible for all my problems with too much gas to No.2 or does it also sound like I have a possible float problem with that carb? I don't have anything to compare it to, but the float needle looks clean and seems to operate ok. Finally, with all the fuel dumping, should I worry it's in the oil?

Ok, nuff for now. Don't want to wear out my welcome. Thanks guys.

[chef1366]

Sounds like a petcock. check and see if there is fuel in your vacuum hose of the petcock. If there is get a new one or rebuild it.

[ruddy]

Check your oil level. If gas is leaking past your floats, it will rise. You can also remove the filler cap and sniff. If gas is in your oil, you'll smell it.

[KEITH KRAUSE]

You probably do have fuel in the crank.
The "painted in" jet you refer to is really a pilot fuel screw. Underneath/engine side of bowl? It assists the pilot jet. The pilot jet is inside the bowl.
If there's no rust or dirt on the #2 float valve, the leak could be a small burr on the side or the valve tip is "grooving" near the tip or the pin/spring is getting weak. Be sure the valve seat has its fiber gasket or o-ring in good condition. Could also be a sticking float, punctured float or float level set to high. Correct height is .94/.95".

[Pearson]

Ok, I got it...everything looks really good in the carb itself and the spring seems to be in good shape, but I also know the float is set to >.95. Between you, ruddy and chef I've got some things to go look at. I'll post in a few days if you're interested in progress. Meantime I"ll get that gasket set ordered for the petcock. That clearly isn't working right. Thanks all.

[Pearson]

It's been awhile since I posted but I've been busy on the bike. Seat is off to Sargents, new superbike bars are enroute. New tires, brakes overhauled. I'm almost there...but for this gosh durn leak. I bought the Pingel, installed it last night (top notch product!) got the bike started and I'm still leaking fuel from the bottom of No.2 carb, 1 per second.

I routed the drain hose into a bottle and started the bike on the center stand. As I added choke and revs increased, if I looked real close, the fuel started draining faster. I tapped on all 4 bowls but it didn't stop the drip. The higher the revs, the more comes out.

I have completely rebuilt the carbs with bonafide rebuild kits, scrubbed everything I could, replaced all the gaskets and o-rings, gone through 2 cans of air. The carbs are spotless. Once the bike is warm, she idles nicely at 1100rpm. Just a touch of starter and she jumps to life so I suspect my bench sync is pretty close. The unused vac. line is capped off (tho not tightly just yet). Oh, I took all the floats and floated them in gas for 5 min. each, and they all floated just fine. As I said, seats and springs are all new.

Could it be that I'm doing my float level all wrong? I admit, that's about the least precise setting I have but they're all pretty close. I didn't do the carb dip but 2 cans of carb cleaner later, is it possible there's a passage at the bottom of the pilot circuit that could cause a plug I can't see?

[rustybronco]

take the # 2 bowl off and fill it with water to just below the stand pipe and see if it leaks, it could be a crack in the tube or bowl.

[Pearson]

take the # 2 bowl off and fill it with water to just below the stand pipe and see if it leaks, it could be a crack in the tube or bowl.

Haha! I was doing a search when I came across your other post on this...didn't connect the two. I make no apologies though, I'm gettin bout freakin' desperate and $300 less in my pocket...with no improvements

I was talking it over with a guy at lunch...
The bike starts and idles pretty good for a bench sync. That suggests all the jets are fine.
When I increase throttle, more fuel flows out of carb2. That suggests a float problem to me. I'll take the carbs off again and check to see if there's a crack in the tube.

[Jethro]

To properly check your float heights, find a way to connect some clear hose to the float bowl drains. I took 4 old float bowl drain screws, drilled 1/8" holes through the center of them, then drilled 1/4" holes halfway through them. Then I use 4 small pieces of 1/4" brass tube sections and hammered them into the screws. Attach some clear line to them, route the line up towards the top of the carbs and turn on the gas, fire up the bike and see where the fuel sits. It should sit within a few mm of the gasket surface for the float bowl. Using the bench setting method for the float heights is just a guideline, I found my floats were way off. The float valve needles can vary in height slightly due to the springs in them, and the arm of the float can compound the error.

Basically, the only way the carbs ever can leak (presuming the body isn't cracked, and the drains have decent gaskets) is from the float valve not operating properly. That is the only way gas can raise to the level of the carb throat.

Just FYI, something else is amiss. Even if your carbs overflow it should either dump the gas into the crankcase, or back into the airbox (where a drain line is there for that purpose). If you actually see gas leaking from one specific carb, you have bad seals at the carb and/or airbox rubber boots.

[KEITH KRAUSE]

I would think the float level is OK because I assume you adjusted all four by the same method and the other three don't leak.
Is the fuel overflowing out of the overflow line? Meaning the tube connected to the bottom of the float bowl, correct?
If so, then it would be one of the following...
I'll mention everything even if you've checked or it's unlikely in your case?
Debris between the float needle valve tip and the seat.
Float needle valve tip "grooved" or worn. Replace.
Float needle valve spring weakened or broken. Replace.
Float needle valve has a burr on its side, causing it to stick "open". Remove burr carefully.
Wrong float needle valve. Replace.
Float needle valve installed upside down.
Brass seat for valve has a torn or missing fiber or metal gasket. Replace.
Bad/incorrect o-ring for float needle valve, if you use that style. Replace.
Incorrect float level. Set yours to .94"
Sticking float. Check for smooth movement. Make sure the float pin is inside both towers evenly to avoid cocking to one side.
Punctured float. Shake it and listen/feel for fuel inside. Check by submerging the float in fuel for 10 minutes. Replace if punctured.
Bent float arm. Is each side of the float the same height? Bend it correctly.
Also, the float bowl vent line at carb #2 must be clear, not kinked, and routed under the seat. Correct if not. Make sure of carb #4 vent line also. This applies to stock intake only, not pod filtered bikes. I mention this because the bowls must vent well to maintain a constant fuel level, among other reasons. Also, some owners have said they thought the two vent lines should be connected. They should not be connected.
That's about it for what can cause #2 only to overflow out of the overflow nipple/overflow line.
If you're somehow not sure of the leak origin, try swapping #1 and #2 bowls and see if the leak follows.
If bowl related, it would have to be a crack in the bowl, a dirty bowl gasket surface, or the bowl wasn't installed right. I've seen some owners not seat the bowl just right and it will leak, but the leak will be obviously coming from the bowl edge, not the overflow line.

[Pearson]

Thanks Jethro and Keith. I'm working on it right now. Keith I appreciate your patience 'cause I know you've answered these same questions a thousand times.
The fuel is coming out of the lowest nipple on the bottom of carb 2. Per your previous suggestions back in the summer, I've rebuilt the carbs with 4 new kits including the o-ring kit available from another member. All new jets, needles, gaskets, seats, etc. I've tested each float in gas for 5 min. ea. and none sank. Per RustyBronco I filled the bowl with water and no leak. I checked the Clymer and needle valve is not upside down. Float pin was centered. The operation seems smooth except near the end where it seems to require just a tiny bit more force to "seat" (the only way I can describe it). I'll check the others to see if that is consistent in all 4. The floats are adjusted per PaulMusser's VM carb rebuild paper. My ruler only does 64ths so I set it to just a skosh below 1". With the carbs upside down, tab just touching the needle and gasket removed I adjusted all 8 individual floats as above. I spent alot of time trying to get that just right.

I have not reconnected the airbox or most of the vent lines. However when I first started tracking this problem down, everything was connected and installed. Could an air leak really be the cause all this time?

Update: I just took off all the rest of the bowls and No.1 floats are obviously higher than all the others. Also, checking my math, .94 = 60/64th's right? That would mean I was setting my floats too high in addition to No.1 being higher than the others. I'm going to do them all again.

[demark]

If you really want to eliminate (or identify) a hardware issue, swap the floats, float needles, gaskets, and bowls between carbs 1 & 2.

If the problem stays with #2, you can be pretty sure it is not with those pieces.

- Tony

[Pearson]

Guess I"m going to start swapping things around next. I just got done setting the float height again (I spent a solid hour) and no change. Gas still dripping 1 per sec. AAAARRRRGGGHHHH!

[DaShadow]

I had the same problem with my 82 GS650E

hey i was having the same problem out of my gs 650. i didn't have alot of money to put into the bike at the time and i had to get it rolling.
(The quick fix!) I used a brigs and stratin inline fule cutoff valve and an inline fuel filter. the filter is just a good idea on any bike and the valve will take care of the free flowing fuel. if you splice the valve in to your fuel line about 3.5 inches down from the tank, the valve handle will stick out just under the tank and infrom of the side cover(650E) in front of the airfilter box on the larger bikes. it's not the best way to do it i'm sure, but it saves you some trouble. and i'm not sure why the #2 carb is always the one to leak...but that stoped on my bike as soon as i got the valve and installed it. the valve can be found at any small motor repair shop. the metal one is alot more money but the plastic one is working for me just fine!

[Pearson]

hey i was having the same problem out of my gs 650. i didn't have alot of money to put into the bike at the time and i had to get it rolling.
(The quick fix!) I used a brigs and stratin inline fule cutoff valve and an inline fuel filter. the filter is just a good idea on any bike and the valve will take care of the free flowing fuel. if you splice the valve in to your fuel line about 3.5 inches down from the tank, the valve handle will stick out just under the tank and infrom of the side cover(650E) in front of the airfilter box on the larger bikes. it's not the best way to do it i'm sure, but it saves you some trouble. and i'm not sure why the #2 carb is always the one to leak...but that stoped on my bike as soon as i got the valve and installed it. the valve can be found at any small motor repair shop. the metal one is alot more money but the plastic one is working for me just fine!

Yeah, I've been reading bout that too but the carb is leaking with the engine on or off. I just did take my inline fuel filter off and ran some new hose to see if it made a difference (it didn't). Since I converted to the Pingel petcock, isn't that really the same thing as having the fuel valve or are you talking bout something different? Thanks for the input.