VM 26 carb #3 leaking overflow GS 1000

[jknappsax]

I've been trying to figure out why I have gas leaking out of the overflow of carb #3. The carbs have been dipped, rebuilt, the floats set properly, the needle valve and seat changed, and I haven't been able to find the source of the leak. I pulled all the float bowls to look for about the 50th time, and noticed a difference in in carb 3, which has what looks like a check valve in the left hand hole that comes from the vacuum inlet. This is carb #3.

The others seem to have this ball valve up inside this passage.

I can't find anything about this in my factory manual, Clymers, or the VM rebuild series in the forums. Anybody have any info on this? Any help would be greatly appreciated.

[jknappsax]

I can't seem to upload both pix, so here is the other one. This is carb #2, and #1 and #4, which don't leak.

[Nessism]

The vent ports are ganged together so the carbs can use them in pairs. No. 1 and 2 share and 3 with 4. You might want to blow air though the vent ports to make sure the carbs are venting properly. It doen't seem right to have only one carb with the vent tube blocked on one side.

[jknappsax]

What is the mechanism involved with the vents/vacuum? If I look into the carb throats, there are passages at about 2 o'clock and 8 o'clock that are associated with the two vent holes in the top of the float bowl chamber. The one in the #3 carb below the vacuum nipple has the ball visible, the rest of the vents have the ball up inside; I can see the ball in the air mixture screw passage in the right-hand hole in the carb throats. Is there a spring behind the ball in the passage below the vacuum nipple on carb#3? I've never been clear on the vacuum connection/vent tubes situation; they seem to be vents on carbs #1 and #2 that are ganged together, a vacuum connection on carb#3 that is ganged to the vent on carb #4. Any good clarification would be greatly appreciated.

[Nessism]

I don't have a set of VM's in front of me so I'm guessing a little here...

The carb castings have nipples for vents on both sides but Mikuni only drilled the passages on the side as needed. The #1 and #3 carbs have an open vent on the right side of the carb body and #2 and #4 vents on the left side. Those plugged holes visible from the underside are feeds for the vents I believe - the appropriate side should be open to feed the vent port on that side.

If you put a piece of hose on the vent tubes you should be able to blow air inside and figure out there the passages are. Make sure the vacuum port is seperate from the vents.

Hope this helps and good luck.

[Steve]

I was going to ask to make sure you are numbering the carbs correctly, but I see that you already know that the vacuum nipple is on carb #3, so you are doing that correctly.

Have you tried checking your petcock? If the petcock leaks it will come down the vacuum tube into carb #3, making it overflow.

.

[jknappsax]

The petcock doesn't leak down the vacuum line; I have the same symptom if I use the external fuel tank that I use for carb syncing. The PO told me that he'd had a problem with cylinder #3 fouling it's plug, so this might have had some kind of problem since I got it. I STILL want to know what the story is with the ball in the left-hand hole (looking at it from the bottom) above that carb's float bowl. Any other ideas?

[srsupertrap]

Can you add some additional pics with some arrows (paint or Word) pointing to this check valve or ball valve for clarity?

The Suzuki GS1000 manual goes into a theoretical discussion on how your GS1000's carbs operate (choke) but it does not specifically point to individual carb compenents stating which ones do what when. You may want to review the GS1000 service manual on Basscliff's website . . .

[duaneage]

For fuel to flow either it has to be drawn in through the well and choke circuits or else the float system is faulty. Looking at the body it's clear there is no dirt present (that body is cleaner than my kitchen table) and the needle looks new.

I would put the float in a jar of gasolina and see if it

wait for it


floats.

[Steve]

Can you add some additional pics with some arrows (paint or Word) pointing to this check valve or ball valve for clarity?

Here is what I believe he is talking about:





.

[Steve]

Looking at the body it's clear there is no dirt present (that body is cleaner than my kitchen table) and the needle looks new.

Please pardon me if I don't eat with you, Duane, but here is what I am used to calling "clean carbs":

[Pearson]

Here is what I believe he is talking about:





.

Forgive me, I don't have this carb but I see the tall tube, out of focus in this pic in the lower right hand corner. This is the overflow tube? Mine had a hairline crack almost invisible. I filled the crack with solder and hasn't leaked a drop in 2.5 yrs.

[duaneage]

Please pardon me if I don't eat with you, Duane, but here is what I am used to calling "clean carbs":

I didn't say they were cleanest or cleaner than yours. I said they were cleaner than my kitchen table. If you have a 4 year old you know what I mean.

[duaneage]

Forgive me, I don't have this carb but I see the tall tube, out of focus in this pic in the lower right hand corner. This is the overflow tube? Mine had a hairline crack almost invisible. I filled the crack with solder and hasn't leaked a drop in 2.5 yrs.

That is not the overflow tube, looks to be take up for the choke circuit.

I'm not an expert on this particular model of carb(or any other really) but as a practical matter he has three that work and one that doesn't so this should not be hard to determine.

[duaneage]

Found the trouble, the vent tube was leaking at the base of the bowl, small hole was letting gas in. When he turned the fuel off and it continued to drip without additional fuel entering the bowl we retested the bowl (after drying the fuel out) and sure enough the brass tube failed.

Is it possible to drive them out and replace them? Are they available?