2003 gs500
Cleaned the carb float bowls and then had several fuel lines split and the T nozzle inlet on the carb broke. Replaced the T and the hoses. Now when I start the bike it will run for a couple of minutes then dies. Have to wait 5-10 minutes before it will start again.
Tried running with the tank cap open and checked the tank breather hose, no difference
Checked the ignition coil resistance as per this thread:
http://gstwins.com/gsboard/index.php?topic=19546.0
Got 4.5 Ohms and ~32k Ohms which seems high, but within the correct range.
My guess is it's related to fuel supply. The hoses I used for the fuel line were 1/4" so slightly smaller than stock.
Any ideas?
I would guess the float level is too low, or as you suggested, the fuel supply is weak due to too-small hoses. Could also be a vacuum leak causing the petcock to not stay open while it's running so not enough fuel makes it into the carbs.
Might as well pull the carbs again and reset the float height, then when you put it back together, use the right size fuel hose in the process. IIRC one of the hoses from the factory is one size on one end and another size on the other. But I think they are all like 7mm nominal, right? Which is just a little bigger than your 1/4".
You lose 1 cyl then it stalls or both ?
So if its 1 cyl - It could be those 2 coils. They have to be close together, not 1 8x the other.
One may be heating up and not sparking. So trace it to what coil and if swapping coils side to side makes it switch cyl.
Sorry about that - didn't realize you were measuring the primary and 2ndary of the trigger coil, thought you were measuring the spark coils left vs right. However the rest of the diagnosis sorta is the same. Find if you lose 1 cyl or both first. A quick touch of the exhaust will tell you.
Now if it is both cyl, and carb related, I'd almost guess you have a vacuum lock problem where that upper T in the top rear of the carb isn't free to take in air. AKA your bowls aren't filling at the speed you need to keep them where they will run.
BTW 03 - I take it you're not in the US ? I'm not sure of the exact carb you have, but find out which carb has vacuum line, make sure that is good, and the T for air vent again not sure if it wasn't exactly where I said it is.
Cool.
Buddha.
Quote from: The Buddha on August 07, 2021, 04:27:21 AM
You lose 1 cyl then it stalls or both ?
BTW 03 - I take it you're not in the US ? I'm not sure of the exact carb you have, but find out which carb has vacuum line, make sure that is good, and the T for air vent again not sure if it wasn't exactly where I said it is.
Lose both at the same time, it takes less than a second to slow down then stall.
I'm in Aus. Interesting you mention the vacuum line because my bike never had one. I thought it was weird that nothing ever connected to part of the petcock, although I don't remember looking prior to this whole ordeal.
Is it possible all of my troubles started when it somehow fell off? (Original problem was spark plugs that got so coated in carbon in three weeks, from brand new, that they wouldn't spark)
LOL, I know all 3 gens of carbs well, but that fuel tap looks like its a part off the space shuttle bro. I'm out. Someone who knows what that contraption is should be along soon.
Cool.
Buddha.
Quote from: Derifity on August 07, 2021, 12:25:52 PM
Quote from: The Buddha on August 07, 2021, 04:27:21 AM
You lose 1 cyl then it stalls or both ?
BTW 03 - I take it you're not in the US ? I'm not sure of the exact carb you have, but find out which carb has vacuum line, make sure that is good, and the T for air vent again not sure if it wasn't exactly where I said it is.
Lose both at the same time, it takes less than a second to slow down then stall.
I'm in Aus. Interesting you mention the vacuum line because my bike never had one. I thought it was weird that nothing ever connected to part of the petcock, although I don't remember looking prior to this whole ordeal.
Is it possible all of my troubles started when it somehow fell off? (Original problem was spark plugs that got so coated in carbon in three weeks, from brand new, that they wouldn't spark)
well, that petcock which in the picture works with vaccuum, which (most likely) connects to that upper inlet of the diaphgram valve....vaccuum opens the valve and fuel flows to carbs etc etc.. you know the deal.. in case the diaphgram is slighlty broken it lets the fuel drip to carbs even without vaccuum, and when engine is started it just uses the fuel in the bowls and cuts out..if you dont have the vaccuum hose connected to it.. surely you have a vaccuum port in the carbs, the left one to be specific.
Did something a little dodgy and got an answer. Found a guy who was selling a 2003 gs500 around the corner from me, went to have a look at the correct setup (he was nice about it, but clearly a little pissed.)
The vacuum hose that runs from the right carb to the petcock isn't connected and is also far too short to reach but that would explain the engine running then dying, and only restarting when enough fuel has trickled back in.
Still no idea at what point this got disconnected and how it is about 200mm short...
Actually looking at the diagram the vacuum hose runs from the inside of the left carb. Is the hose running out of the right a drain hose like I first suspected? can't find it in the manual or diagram.
I think the vacuum hose never existed on my bike...
so here is a 2004 gs500f carburetor, the hose highlighted is the hose going to the petcock. there is also a diagram I found the diagram for 2002 GS500 (https://www.bikebandit.com/oem-parts/2002-suzuki-gs500/o/m22461#sch246381) and 2004 GS500F (https://www.bikebandit.com/oem-parts/2004-suzuki-gs500f/o/m6061#sch503304)(My bike). In my case (04 gs500f), the hose labeled 73 is the one that goes to the petcock in the link. Hope this helps
(https://i.imgur.com/MSOujUVh.png)
Thank you mentalshark, looks helpful although the top half of the carb looks very different from mine.
If the highlighted hose is the vacuum hose that connects to the petcock, where does the T-junction go?
Also, what is the part I circled? The other 2003 GS I had a look at had it as well but my bike doesn't...
QuoteIf the highlighted hose is the vacuum hose that connects to the petcock, where does the T-junction go?
From what I can find here is how I think it works:
The engine is sucking air and the tube from this side of the carburetor have a suction and have a hose connected to it. The other side on the carburetor is just capped off. This vacuum does two things hence the T joint.
One hose goes to the petcock to and operates the petcock to let fuel through. Without this the petcock didn't know the engine is running and therefore won't be able to provide fuel to the carburetor. You should be able to have the petcock working if you turn it to PRIM, which means ignore the vacuum just give fuel.
The other hose is connected to the bottom part where has 2 vacuum hoses coming out of it, that is a solenoid controlled by the CDI which I don't fully understand how it operates. But this very CDI is also connect to the thing you circled which is a throttle position sensor. I think the CDI is doing ignition as well as emission control. for the emissions controller part, in some scenarios it would open the solenoid, which will lead to this engine created vacuum to open the diaphragm on top of the carburetors(the white plastic cap on top), this will then cause the air going into the carburetor from one of the venting hose (a small filter with a short tube connecting to both carbs). Since the plastic slide is operated by vacuum, the slide will drop due to the air going in there, therefore closing the valve and restricting the airway.
here is a video of the guy explaining that top white port https://www.youtube.com/watch?v=FyA-L5XIYpo&ab_channel=GeoffreyMarsh (https://www.youtube.com/watch?v=FyA-L5XIYpo&ab_channel=GeoffreyMarsh)
This is just my understanding of how this works... All these information comes from the internet last night as I was researching about the bottom solenoid. I am really new to this as well (just got my first bike last month) and just sharing the information that I found.
My carbs look very similar in some ways, but mine doesn't have that black sensor or the white ports. Even the other 2003 I had a look at had the black sensor which makes me think something's up with my carbs, never caused problems before.
Thank you for the deep dive mentalshark!
Hose running off the right carb was the vacuum hose, just had to run it over with the air box off and now it runs perfectly.
Thank you all for your help, now I just have to deal with the fuel in my oil!