Hey guys, my bike runs only on the PRI position. So my guess is it's just a disconnected vaccum hose. I took the tank off , and found 2 disconnected hoses, one at the bottom of the tank (Fuel overflow?) and the other is shown in the first picture. question is, where do they go? i think the one at the bottom of the tank doesn't go anywhere, but what about the other one. there was also a sealed hose at the bottom next to the battery breather, is that the eay it should be. it had a cut at the bottom so maybe that was the cause of the problem. Anyways, the repair manual is on the way, but i need to get the motorcycle runing ASAP. thanks. the links for the pictures are below.
http://filebox.vt.edu/users/mkhalil/Pictures/HPIM0683.JPG
http://filebox.vt.edu/users/mkhalil/Pictures/HPIM0684.JPG

For starters, see my Fuel Hose Routing page.

The large hose in your first picture simply drapes over the airbox into the relatively quiet air near the battery.  It is supposed to be open to the air, because it supplies a "reference level" of atmospheric pressure to the carbs.

The hose in your second picture is the drain hose from the airbox.  (See the diagram at the bottom of my page.)

The small hose underneath the tank is another drain hose:


So where's the vacuum hose?  On an '89-'00 bike it is a smaller-diameter hose that goes from the frame-mounted petcock to a port on the inside of the left carburetor, as described on my page.  But JohNLA gave me to understand that on the '01+ models the vacuum hose goes to the outside of the right carb instead.  In your first picture this hose is visible between the right carb and the wiring harness.

If that hose is connected securely to the right carburetor, make sure the other end is connected to the frame-mounted petcock.

Okay, so everything was connected according to your diagram. there was some fuel in the airbox drain hose and why did they cap that hose? should it be sealed or something?

I can only guess why the airbox drain hose was designed with a slit cap on the lower end.

1) It allows you to control (to some degree) when and where the contents of the hose get dumped.

2) It allows you to get some idea of how much (if any) blow-by has been collecting in the airbox.  If the hose drained freely, you might lose some useful information.

Again, just my guesses.

Okay, so all the hoses are straight, but it still runs for a few mins then cuts off when the fuel valve is on the ON postions. what could that be?

You haven't said how much fuel is in the tank.  If everything is hooked up correctly, and the whole fuel delivery system is clean (in-tank filter, hoses, petcock, float valve assemblies) then the only thing left is a lack of fuel.  By that I mean that there isn't very much fuel in the gas tank.

QUESTION: How long does the bike run if you turn the petcock to the RES position?

In my experience (I got "bit" by this the very first day I had my bike) it can LOOK like there is plenty of fuel in the tank when in reality there isn't enough to run the bike in the ON position.  ON should take you from full to about the "1 gallon to go" level.  RES (reserve) should take you through much of that last gallon.  But if it gets lower than that, you're down to PRI or pushing.

Tank is half full. Now it doesn't even start. it cranks but that's all. I think I've killed my bike  :x

According to your post in the Fuel switch thread you've been having this problem since early November?  Yikes!

Can you drain fuel from each float bowl (in the PRI position)?  Does it come out at a good rate?


It sounds like you either need to:

A) Clean the whole system, including the innards of the ON/RES/PRI petcock.

B) Get a new ON/RES/PRI petcock, depending on what you find during the cleaning.

C) Bypass the ON/RES/PRI petcock by attaching the front (RES) hose from the tank-mounted petcock directly to the lower T-connector between the carbs.  You would also need to cap off the other (ON) hose.[/list:u]Keep us posted....

Yeah, I've been having this problem since I bought the bike in November, but I spent the last six months out of the country, and now, I wanna ride. Anyways, fuel comes out a good rate. Does that eliminate anything, or should I still go for all three of your suggestions? Thank you so much for your help so far.

"Lemme 'splain ... no, there is no time ... lemme sum up."

If I understand the situation, you're just getting back after a 6-month "away trip" to a bike that had fuel delivery problems BEFORE the trip.  If I read between the lines correctly, you haven't really ridden the bike since getting back.  This is because the bike won't start, or won't run for long when it does.

Correct so far?  (If not, let me know.)

The thing I'm trying to reconcile is that you originally said the bike would run in the PRI position but not (for long) in the ON position.  But now the bike won't even start?  I'm not sure whether to have you clean out the fuel system and start over with fresh gas, or to start testing for spark and other ignition problems.

If the float bowls drain freely with the petcock in the PRI position, then bypassing the petcock altogether shouldn't act much differently.  So put that diagnostic on the back burner for now.

Tell you what.  Since you SEEM to have good fuel flow in the PRI position, start by checking for a good spark on both cylinders.  (You're familiar with how to test that?  If not, let us know.)  Also, how do the spark plugs look?  Pick the closest sample from the Haynes spark plug chart.

If the spark looks good, then I suggest that you go ahead and clean the carbs and the innards of the frame-mounted petcock.  As part of that process, drain the tank and put in new gas.  (Use the old stuff in your lawnmower or something.)

We need some more clues before we can "nail" this one.  So you'll have to try one thing at a time and report on the results.  OK?

KERRY, YOU DA MAN!!!!! okay, here's the story as I figured it. The P.O rejetted the bike, and in the process totally messed up the air to fuel ratio and somehow messed up the throttle, it was stuck half open. He then adjusted the AFR so it would idle fine, but the throttle was still messed up. That caused the bike to run on PRI only. I thought it was a vaccum leak so I started pulling stuff off the bike to find that leak, but I found nothing, so I put the stuff back on, then  talked to Kerry and went to work on it again, when I put everything back on this time, I forgot to switch the tank mounted petcock back to ON, so the bike ran for 5 mins then died. Anyways, I tried to drain the tank as Kerry suggested, but no fuel came out and I checked the tank petcock and voila! I then looked at the idle screw, and it was backed all the way out. So when I messed with it, the bike finally ran on ON fine, but ideled at 5000 RPM so I checked the throttle and it was stuck half open because the cable was stuck. So i got that working, now the bike runs fine. Took it for a 20 mile ride to Home Depot and it ran like a dream, so much more power now. Now, in the spirit of fixing thing, I'll flush the brake fluid, take the chain off and try to clean it. Lube didn't do much to the rust that was on it. Again, thanks a million Kerry.

You're welcome (of course) but apparently I didn't suggest anything close to what the problem was.

Kudos to YOU for keeping at it, and for using your head to unravel what you found!  

First, i have a 1997 (cali model) gs500e.

It worked before i put it in storage (for 2 years - long story)

I got it out and it didn't work. I replaced battery and spark plugs. Now the engine turns over but will not start. I pulled carb out and poored gas directly in the diagaphram and it started for like 5 seconds.

My guess was i had hoses reasembled wrong, but after extensive search on this site (tytytytyty for the pics and diagrams) i had the hoses all assembled correctly after all. (i counld not believe all those hoses just went no where... but they do! - one water drain from tank one vent hose from upper t connection... i spent hours trying to figgure out wher i went wrong cause i just KNEW they had to plug in somewherel.... lol

I just tried the drain fuel from each float bowl (in the PRI position) and got 3 drops on the left and 5 on the right carb... so i am not getting fuel... but i know i am getting good fuel to the petcock as that is how i drained the tank of all the old fuel.... so i guess i need to dissasemble and clean petcock next... (and maybe do extensive carb deconstruction cleaning? please say no!!!!)

Am i on right track? any suggestions? I really really want to get my bike running again!

ty!!!!

Quote from: pianoprazeso i guess i need to dissasemble and clean petcock next... (and maybe do extensive carb deconstruction cleaning? please say no!!!!)

Well, my vote is YES.  Cleaning the carbs isn't too bad with a Clymer or Haynes manual.

But first ... did you have the petcock on PRI (pointing UP) when you tried to drain the float bowls?

I've never had my petcock apart, so I couldn't say how likely it is that it's gummed up.  But the float valve almost SURELY is....  

I would take the frame mounted petcock off and test it with water. It also doesn't hurt to check the tank mounted petcock. I know you drained the tank and all so it must have been on, but you never know when you're gonna do something that's not-so-smart (no offence) for no reason at all.

I ordered the gs500 manual from clymer off amazon, so i will do a full cleaning when it arrives. Yes i had petcock to prime. After taking it apart i do think there is a problem because i could only get air through petcock (in the on position) when the arrow at 7-8 o'clock.. not 6 licke it should be for the on position...... is that normal? need replaced???

I tested the tank petcock and it works fine aerospike