fuel in the petcock vacuum line to the carb **UPDATE**

[rockstar]

I don't have a 550, I have a 450, but I've been looking for an answer to this question all day and you guys seem to know what your talking about. My bike has a nasty idle problem. I can get to idle around 1200, If I play with the idle screw, but once I rev up the bike it wants to stay a 3K and I have to adjust it over again. it'll work fine for a little sometimes, where I can rev it and the idle goes back down, then it starts acting up out of nowhere.

I was messing with it this morning and I noticed the vacuum line for the petcock (not knowing it was a vacuum line) didn't have fuel going all the way to the carb. it had a inline filter which I removed thinking that maybe it's clogged. removed it and put in a vac. T and cap just to see if it'll help and the fuel stays and the same place just before the vac. T. There shouldn't be any fuel in that vacuum line from the carb to the petcock right?? I was thinking maybe the petcock is messed up, leaking internally, draining back. if this doesn't make sense I can try and explain it better.

[DoD#i]

If there is fuel in a vacuum petcock vacuum line, then the diaphragm in said vacuum petcock is bad - time to replace it.

[rockstar]

would a rebuild kit help??

[The Buddha]

Make sure it has that little diaphragm. Most kits I have seen do ... 
Heck there is that and 1 O ring in that petcock, but yes you have a tiny rip in it. I had one, bike starts and runs great but 5 mins in it will quit running at idle on that cyl. It will run on both, just not idle on both.
Cool.
Buddha.

[rockstar]

Make sure it has that little diaphragm. Most kits I have seen do ... 
Heck there is that and 1 O ring in that petcock, but yes you have a tiny rip in it. I had one, bike starts and runs great but 5 mins in it will quit running at idle on that cyl. It will run on both, just not idle on both.
Cool.
Buddha.

ok thanks, I'll tear it apart tomorrow and see what's damaged.

[rockstar]

one more question, there's not supposed to be a filter in the vacuum line right? or the fuel line cause there's the filter on the petcock?

[rockstar]

ok, I just went out a did a few tests.

what I thought was the vacuum line is the fuel line.... so I got out my vac. pump and test the valve in the on and res. positions. with a vacuum apply to the vac. line the reserve spits fuel out the line just fine. but when I turn the valve to on the fuel flow stops?? prime works. The funny thing is that the bike starts and runs with the valve in the ON posiiton.

another thing is I think my line isn't routed that great where it's getting a downward slope to get to the carb, which I could fix, but that valve doesn't make sense. I really don't know how these petcocks work internally, would I have to get a new one or would a rebuild kit help this?

[DoD#i]

If there is a rebuild kit available and it includes the relevant parts, should work fine. What I've gathered here is that for ours, there apparently isn't one. For yours, if there is, it should do the trick - if, in fact there's actually a problem with it, which issue you've now confused...

[The Buddha]

ok, I just went out a did a few tests.

what I thought was the vacuum line is the fuel line.... so I got out my vac. pump and test the valve in the on and res. positions. with a vacuum apply to the vac. line the reserve spits fuel out the line just fine. but when I turn the valve to on the fuel flow stops?? prime works. The funny thing is that the bike starts and runs with the valve in the ON posiiton.

another thing is I think my line isn't routed that great where it's getting a downward slope to get to the carb, which I could fix, but that valve doesn't make sense. I really don't know how these petcocks work internally, would I have to get a new one or would a rebuild kit help this?

You need vacuum for on as well. Only prime will be non vacuum.
The vacuum line getting fuel due to hole in the diaphragm, will not neccesarily stop it from running in on or res position. The vacuum in the line will open the petcock and take in a wee bit of fuel when the diaphragm rips a tiny one. If it was very big rip, then no fuel flow in on or res.
Cool.
Buddha.

[rockstar]

ok, I just went out a did a few tests.

what I thought was the vacuum line is the fuel line.... so I got out my vac. pump and test the valve in the on and res. positions. with a vacuum apply to the vac. line the reserve spits fuel out the line just fine. but when I turn the valve to on the fuel flow stops?? prime works. The funny thing is that the bike starts and runs with the valve in the ON posiiton.

another thing is I think my line isn't routed that great where it's getting a downward slope to get to the carb, which I could fix, but that valve doesn't make sense. I really don't know how these petcocks work internally, would I have to get a new one or would a rebuild kit help this?

You need vacuum for on as well. Only prime will be non vacuum.
The vacuum line getting fuel due to hole in the diaphragm, will not neccesarily stop it from running in on or res position. The vacuum in the line will open the petcock and take in a wee bit of fuel when the diaphragm rips a tiny one. If it was very big rip, then no fuel flow in on or res.
Cool.
Buddha.

there's no fuel getting into the vacuum line. I made a mistake. I took off the tank and applied vacuum to the vacuum line with petcock in the ON and reserve position. fuel will come out when on reserve, not when ON. I took the petcock out and filter was clean. could it just be that I don't have that much fuel in the tank that it doesn't work? it starts and idles when ON too though, so I don't think that's the problem

Really the only problem now, is that it idles fine at about 1200K. but one I rev it up it'll stick at 3K or so. adjust the idle. rev it, same thing. it'll also slowly start raising up to 3K by itself..... I backed off all the linkages at the throttle and on the carb so that wouldn't interfere and it still does it.

[DoD#i]

Smells like float height - too high.

As for the "starts and runs in 'on' ", how long have you been leaving it running - what's in the carb bowls will start and run for quite some time, so you may just have low fuel in the tank.

[The Buddha]

No Dod ... its air screw - open it 1/2 turn. You're lean. How do plugs look at idle.
Cool.
Buddha.

[rockstar]

Smells like float height - too high.

As for the "starts and runs in 'on' ", how long have you been leaving it running - what's in the carb bowls will start and run for quite some time, so you may just have low fuel in the tank.

well, the first thing I had wrong with this bike was the stator and rectifier. I just recently installed new ones 2-3 days ago now. but prior when I had the charging issue from when I've bought it I've always had it in the ON position. I drove it atleast 40 miles with a full tank of gas.

No Dod ... its air screw - open it 1/2 turn. You're lean. How do plugs look at idle.
Cool.
Buddha.

I don't think I have an air screw, cause I've taken it apart already and I could find one. it's this carb
http://cgi.ebay.com/ebaymotors/Suzuki-GS450-80-Carbs-Carburetors-068780_W0QQcmdZViewItemQQcategoryZ10066QQihZ001QQitemZ110283744122QQrdZ1QQsspagenameZWDVW

it's kinda hard to see it all. how do you look at the plugs when it's idling??? I haven't even look at my plugs yet. in the first picture on that link they show 3 nipples. the lower is for the fuel and the 2 upper I have just vent done towards bottom of the bike. are those supposed to be vented??  Another thing I was thinking, was possibly back pressure or the throttle slide not returning fast enough or maybe like a valve. I'm going to pump my vac. gauge on it and see there's anything weird. that port for the petcock get's vacuum from both carbs or just the one it's connected to?

[fasterlapdunn]

I wanted ressurect this thread.  I am going thru the same thing with this 1994 gs500.  I have been beating my head for 3 weeks now.    The bike ran well before I touched it...spark plugs looked fine.  I took the tank off to look at the air filter.  I put the tank back on...bike starts up idles at 1200-1400.  Rev it up the idle hangs at 3k-4k.  THere is only 2000 miles on the bike so I am leaving valves out of the equation.  Buddha told me about the lean theory, vaccum leaks and all that.  I have even went to Buddha's house to get this thing to work right but we ran out of time. The carb has been cleaned and tuned for the lean condition, the gas tank has no debris in it and there are no vacuum leaks.  Once the before mentioned things were completed the hanging idle was gone but the bike had hesitation out of first gear as you took off.  Buddha told me that now I was too rich...fuel screw issue...cool...no problem.  BTW I have a DJ kit. 

So this thread relates to me because before i went to fix the too rich scenario I decided to replace the fuel lines with clear ones and a new fuel filter.  Guess what happened when I put it back together??  Hanging idle was back.  So, my vacuum petcock is the culprit I beleive.  It does not work on fuel period...you can see that it is not drawing in fuel with the clear lines.  It works on reserve but on the highway it stumbles.  On prime it is great everywhere.  I think i need to go to the pingle set up to fix my problem...

What do you guys think,  I am just looking for some reassurance here...your reply is greatly appreciated.  And I was going to do the whole to whole measurement for the pingle setup...is there someone with experience with this pingle setup that can tell me the correct distance between the bolt wholes is?  1994 gs BTW 

[The Buddha]

OK the fuel in vacuum line will affect the left carb, and cause it to drown out in fuel and die. It will struggle to hold idle upon being blipped, it will drop below the ide rpm and almost die before it comes back up ... etc etc - opposite of your problem.

Prime will not solve that problem. The one and only problem that prime will solve - OK 2 problems ...

1. and by far its #1 - the vacuum line has a pin hole or somewhere air is getting in the vacuum line. This will cause hovering, and lean condition - more in 1 cyl - left than the other.
2. The petcock is stuck in the 2 other positions even with vacuum. Both issues are with the frame petcock. No pingel for frame - you have to go to a single petcock and that will be very very hard to operate - remember that whole screw driver thing opening the fuel tap in the bottom of the tank - that you have to repeat @ every start/stop.

So - I'd look at the vacuum line, its taking in air somewhere.

Past that, open the frame petcock and clean it and see if it is stuck with vacuum applied also.
Cool.
Buddha.