Touch the gas....it dies!

[BladeRunner]

Bought 1999 GS from my niece. Had been sitting inside for years. Installed a new battery and new fuel lines. Ran at slow speeds but very rough at higher rpms. Discoverd petcock vac line was not connected as I was in process of removing carbs for a cleaning at the local shop. Now that I have reinstalled the clean carbs and re-attatched the vac line the bike is very difficult to start. Ildes rough and dies if I touch the throttle. Tech told me he set the mixture screws at 1 3/4 turn out. OH, also installed a in-line fuel filter. There is fuel in the filter.
Please help guys....beginning to think I bought myself a bucket of trouble....and this is my first bike.....at fifty-one years of age.   
ps. It only seems to start in PRI position.

[Jenya]

Try to bypass the petcock. GS has a notoriously crappy petcock that causes the fuel starvation problem.
The fact that your bike ran with the vacuum line removed indicates that the petcock is not doing what it is supposed to - shut off fuel when there is no vacuum. It probably doesn't open fully either when there is the vacucum.

The purpose of the vacuum operated petcock is to shut off fuel when the engine is not spinning. It is a safety feature designed to prevent drainage of the fuel tank on the ground if the floats in the carbs are stuck for some reason.

In any case, it is easy enough to bypass the petcock and see how the bike runs without it.

Jenya

[beRto]

Bought 1999 GS from my niece. Had been sitting inside for years. Installed a new battery and new fuel lines. Ran at slow speeds but very rough at higher rpms. Discoverd petcock vac line was not connected as I was in process of removing carbs for a cleaning at the local shop. Now that I have reinstalled the clean carbs and re-attatched the vac line the bike is very difficult to start. Ildes rough and dies if I touch the throttle. Tech told me he set the mixture screws at 1 3/4 turn out. OH, also installed a in-line fuel filter. There is fuel in the filter.
Please help guys....beginning to think I bought myself a bucket of trouble....and this is my first bike.....at fifty-one years of age.  
ps. It only seems to start in PRI position.

Don't get discouraged! This doesn't sound like a major problem. 

Bypassing the petcock is a good suggestion to get more information on whether or not that is the problem (although even if the petcock was bad I would expect it to run ok in the "PRI" position).

A few ideas:

• In what condition are the sparkplugs?
• Is the in-tank petcock clean (could be rust buildup, or water)?
• Are you using fresh gasoline?
• Did you set the engine idle when the bike was warm?
• Could the mechanic have lost the little carburetor o-rings when he took them apart?

Keep us posted! 

[BladeRunner]

Thanks brto,
Plugs may be fouled but I doubt it. I will check. Intank petcock hasnt been touched but the bike did run before the carb job. Gas is fresh 93 octane. As for the idle screw, after I re-installed the carbs and finally got the bike to run for a moment I adjusted the screw to 1200rpm but the bike was not warm....so I dont know where I'm at on that variable. I feel the mechanic is competent as to the carb job but who knows.
As for the main petcock, the bike should run on PRI even if it is bad....there is gas in the in line fuel filter which is downstream of the petcock. I may by pass it anyway....getting desparate.

[coll0412]

There is alot of possibilities. But the first that comes to mind for me is water in the gas. Did you drain the tank entirely when adding gas, or did you just top it off.

I have had it happen to me before.


The other thing is a major vacuum leak, or the slides being stuck or something, could be quite a few possibilities.

[BladeRunner]

Slides?

[ivany]

Stupid question...are you using the choke? And is the engine warmed up, i.e. let it run for a few minutes?

[BladeRunner]

Sorry, it is very difficult to start and wont run very long. The choke, or touching the throttle, kills it.  I seem to have the best luck starting in the PRI petcock position.

[coll0412]

I would check the float level.Put the petcock on PRI and put piece of clear plastic tubing onto the nipple at the bottom of the carb bowl, then pull the tubing up and put it so when fuel tries to come out it must travel up the tube. Then slowly loosen the drain screw so fuel starts to come out, it should rise to right where the carb bowl meets the body. This is a crude way to measure the fuel float height(actually the fuel level itself) in the carb.

[GSnoober]

Check this page for photos of the procedure coll0412 mentioned:

http://www.bbburma.net/FloatHeight.htm

Read it, then bookmark it, so you can find it again. Then, open the home page:

http://www.bbburma.net

and bookmark that one also. As you'll see, Kerry (a moderator here) has provided some truly useful material on his website. Don't overlook the FAQ section:

http://gstwins.com/gsboard/index.php?board=7.0

and don't forget the Wiki:

http://cgi.stanford.edu/~sanjayd/gs500/Main

With some time and patience, you'll get this sorted out. I suspect that this might be a combination of a few minor problems, so being logical and methodical will give you the best chance to analyze this, and find a way to resolve it. Whatever else you might do, don't RUSH this; ask questions if you need anything clarified, and double-check your work to make sure you didn't overlook anything, or you'll only wind up chasing your tail all over Hell's Half-Acre (don't ask me how I know).