Petcocks and Such

[Firebirdracer82]

I wrote on here yesterday about my newly acquired 1982 GS 550L basket case. Yesterday, I replaced the fuel lines and filter, looked for air leaks (which I might have missed, since I didn't tighten up the air intake on carbs 2 and 3) and put in my newly charged battery.

I got the bike started on choke and it ran for a time without stalling. Then, after taking off the choke, and with my hand on the throttle (because it won't idle) I was able to drive it a few miles before it started stalling (all the while keeping my hand on the throttle). I could then push start it when it stalled out, it would run for a time, while bucking, and then stall out within a quarter mile.

I noticed on here that if the petcock was bad it might flood the #2 carb, causing stalling. The carbs were rebuilt (not by me, and perhaps badly). I also put on a new-ish clean tank. While doing that, I took the old petcock out of the old tank and cleaned it. It looked like hell, with large amounts of solidified gas. I scraped it out as best I could, but I noticed that there was a small metal part in between the selector and the area where the fuel came into the line. I couldn't figure out what to do with it, and I figured that it was a small broken spring or stop. I put it back together and got gas flowing, believing that it would work ok. The bike indeed started, but won't idle and won't stay running.

My question is this, does anyone think that this could be the cause of my woes? I can easily do this without rebuilding the carbs on my own (scared) and figure that it could be the cause, since the petcock looked so horrible earlier.

Any thoughts are helpful.

[Draketh]

Well, I know for sure if you yank both lines off the petcock gas should not flow in on and reserve, however gas should flow during prime.

Does anyone know if there if a way to test petcocks? Like can I suck or blow into the vacuum line to see if the gas flow during on and reserve is adequate?

edit: if you get gas flowing during on and reserve with the lines unhooked your diaphragm in the petcock went bad. Don't fuss around with rebuilt kits, just replace the whole petcock. It's a $50-60 investment but its better to get it done and not have to worry about it for at least another 25 years.

[Firebirdracer82]

This may seem stupid, but I don't have two lines on it. I only have the line out to the carbs. Is there a line I am missing? I have a line to another thing for the tank (large round brass thing, that I believe is the gas indicator).

[doctorgonzo]

This may seem stupid, but I don't have two lines on it. I only have the line out to the carbs. Is there a line I am missing? I have a line to another thing for the tank (large round brass thing, that I believe is the gas indicator).

Either you have a second line for vacuum, or you have a manual petcock (meaning it has to be turned off manually when the bike is not running. If you have a second hose coming off the petcock, it doesn't go to the tank it goes to carb #2. That nipple on the tank (fuel gauge) just gets an overflow line on it.

[Firebirdracer82]

I think the second line goes directly to the tank to pressurize it. The other line out of the petcock goes to carb 2. When I took the petcock apart, it showed some kind of membrane on one side, and on the other was the selector for reserve, on and prime. There is a kind of line out on the petcock, but no hose with it and no place to connect it. It looks like the petcock here: http://www.bikebandit.com/houseofmot...m6086sch266800

Could a faulty petcock be the cause of my problem? It's the last ditch thing before I think I must pull the carbs.

[Firebirdracer82]

Here is how I have it set up. I have a line from the petcock nipple to a nipple in between carb 2 and carb 3. I am pretty sure that's the fuel rail. Another line goes from the tank, from what I believe is where it is pressurized, into a nipple on or around carb #2. Those are all the lines I have. Is this the correct setup?

I really hope this could be the problem, or at least the petcock.

[doctorgonzo]

Don't know much about 550s, But MOST petcocks have two nipples on them. One attaches to the fuel inlet between carb 2 and carb 3 (on a 4 cylinder). The other attaches to the top of carb #2. The vacuum on this one when the bike is running makes gas flow. If the bike is not running, no vacuum, no fuel flow. If there is no vacuum line on your petcock, then it's a manual one, and it has to be turned off everytime you shut off the bike or else you get a crankcase full of gas.

[doctorgonzo]

Look on top of carb #2. If there is a nipple there, that other line doesn't go to the tank it goes there. The line on the tank is just for a gas overflow. It goes to a hose to nowhere.

[Zook]

The tanks are not pressurized. They are vented. If the vent is blocked the bike won't run.

If you have a manual petcock the vacuum port on the carb for the petcock needs to be plugged or...the bike will have a vacuum leak and won't idle.

[doctorgonzo]

I'd now say 99% chance his petcock is hooked up wrong and he's getting no gas to his carbs because of no vacuum.

[Firebirdracer82]

Ok, so just for review when I go home tonight.

The petcock has what looks like one proper brass nipple to allow fuel out, but it has another thing going out that looks like a place to hook up a hose. It's a long thing that tilts upward at a 45 degree angle (about). That goes into the back of the petcock, on the other side of the membrane from the line the fuel flows from.

Currently, I have one line from carb #2 connected to a large brass circle on the inside of the tank, that I believe was the fuel gauge, but what I also thought pressurized the tank. Perhaps I should have that line hooked up to the back of the petcock on that other thing?

[doctorgonzo]

Recap...
Larger of the two nipples on petcock goes to the fuel T, smaller of the two nipples on petcock goes to a nipple on top of carb #2, nipple on the gizmo on the tank (fuel gauge) goes to somwhere that if your fuel gauge ever blows a gasket the gas will run somewhere other than the hot exhaust.

[Firebirdracer82]

I'm trying to find a picture of my petcock, but the "nipple" on it is a long slender type of thing without a proper nipple like thing at the end. I believe I have blown through it, and it will pass air, if I remember correctly. Does that support your opinion? I looked at the petcock on the GS that you own, and it's more nipple like, but I still think you might be right with how I have this set up, since we appear to share the same type of gas gauge and the tube will go nowhere. The lack of gas may explain the bucking and the dying.

[Firebirdracer82]

It's much like this one:

http://cgi.ebay.com/ebaymotors/suzuki-gt1100-gs1000-gs850-gs750-gs-katana-FUEL-PETCOCK_W0QQitemZ280242676041QQcmdZViewItem?hash=item280242676041&_trksid=p3286.m14.l1318

Though that is not the actual correct one, the other area looks much like the area where I can hook up a hose on my bike. (The one on the bottom there, not the large brass nipple.)

Should I hook up the line from the #2 carb to that nipple and give it a go?

If this works, I am going to be so happy.

[Draketh]

The one tilted at a 45 degree angle is infact a vacuum port and must be hooked up. Take a look at the carb cleaning series to see where to hook the vacuum line up to on the carb.

http://www.thegsresources.com/gs_carbrebuild.htm