Leaking fuel from multiple areas, but not constantly leaking. So confused!

[cobo10201]

Hello everyone, I'm new here so I apologize if I am posting in the wrong place. I have searched multiple times over the past few weeks but I can't seem to find anyone with my specific issue.

I recently purchased a 2007 GS500F. It had been sitting for 6 months before I bought it and ran choppy. I cleaned the carbs and the bike seemed to run fine during a 5-10 minute ride around the block. The bike slowly started leaking fuel out of the nipple on the air box drain hose (1 drop every 2 seconds). Turned out the carb breather hose was pinched under the tank, so I adjusted the placement of the hose and that stopped the drip.

A few days later, I took the bike out for a bit longer ride (20-30 minutes) and when I came home I noticed the bike was idling at about 3000 RPM. I adjusted it down to ~1200 RPM. After the bike sat for about 5 minutes, fuel started leaking out of the same hose from before but much faster (2 drops per second now). I turned the petcock off and drained the carbs to stop the leak, then turned the tank back on and the frame petcock to prime, then took the bike for a 15 minute ride (changed the petcock from prime to on once it started up). Parked it, watched it for 10 minutes, no leak.

Ran normally for ~7 days, then last night I decided it felt like the bike was running a little lean, so on each carb I turned the air/fuel adjuster screw out 1/2 turn. The idle kicked up to 2500 RPM after a short ride, so again I adjusted the idle screw down to 1200 RPM. Fuel started leaking again, but NOT out of the airbox hose. This time it came directly out of the left fuel rail/carb. Again, turned the tank fuel off, drained the carbs, and this time I put the air/fuel screws back where they were. Turned the fuel back on, took the bike for a 20 minute ride, and so far no leaks (been sitting for ~14 hours since the last ride).

I'm wondering what could be causing this seemingly complex problem. My thoughts right now are something wrong with the floats or the float valves, but if that was the case I feel like it would constantly be leaking, not just when messing with the idle screw. My other thought is a vacuum leak, causing the bike to essentially only run on "prime" no matter where the frame petcock is set, but again I feel like that would cause a constant leak.

To replace all the hoses, the petcock, and the float valves, I'm looking at $250 in parts. I know that cost isn't outrageously high, but I'd like to spend as little money as possible.

If anyone has any clue what is going on, it would be greatly appreciated!

[mr72]

If I were you I'd start with just tearing down the carbs and replace ALL of the o-rings. Including the very-hard-to-get-to idle needle (screw) o ring. Order the parts from Buddha or if you want to shop elsewhere I have a good source, PM me.

I'd also replace the float needle valves since they are cheap (like $12 for a pair) and they can both leak and also get stuck.

While the carbs are apart you can clean them thoroughly, inspect the diaphragms and make sure the slides move smoothly then set the float height and put it all back together.

Whole job including o-rings and float needles should only cost like $30 in parts and you should be able to do the whole job on a Saturday afternoon. Then you can rule out o-rings as the source of leaks. It probably won't leak. Plus your carbs will be cleaned and everything set up. While you have it apart you might consider changing the pilot jet one size up, plus the pilot jet is tiny and gets clogged easily so replacing is easier than cleaning. I'd just think of this as "old carb service".

I don't think your problem is the petcock, or any of the fuel hoses. I think you are probably getting one or both of the float needles stuck open and it's flooding and overflowing the float bowl. This is also causing your high idle, I would guess. The reason you have leaks from multiple places is because all of the o rings are shot so once fuel gets to where it shouldn't be the o rings can't keep it form leaking. With good o rings and a leaking float valve you'd just get flooding.

[Watcher]

Sounds like a cut and dry case of floats/needles are out of spec, dirty, worn.

A sticky needle can cause an intermittent leak, and would cause the symptoms you describe.  A slow leak may overflow from the carb body and into the airbox, a faster leak will come directly out of the carb overflow line.
In one of my first bikes (not a GS) it would sometimes go days/weeks without leaking then while riding I'd smell gas, look down, and have a puddle under the bike.  Tapping on the carb bowls would usually clear it up, as this can dislodge a needle that is stuck down.
That's a good way to check.  While it's leaking tap on the bowls with the back of a screwdriver or something.  If it stops it's bad needles.  If it doesn't it could still be bad needles but would also indicate a float out of spec.

The whole service recommended by mr72 might not be necessary, but if the carbs are coming apart to replace the needle/seat and adjust the floats it's not much more work to just change ALL the seals...
It'll be worth it long run if the carb hasn't been serviced, so you might as well for the few bucks.

Re: petcock I'm not sure what you mean by turning it "off".
The factory petcock is a 3-position valve.
"On" and "Res" are vacuum operated and only flow fuel when the engine is turning.
"Pri" bypasses the vacuum and flows freely, and is used to prime the carbs after service or to bypass a vacuum leak issue to limp the bike back home.
There is no "off".

[cobo10201]

Thank you for the response. I took mr72's advice and ordered a set of o-rings. Still looking for a decently priced needle but only seem to find the whole valve assembly. I'll try the tapping if it starts leaking again before the o-rings get here.

Re: petcock I'm not sure what you mean by turning it "off".
The factory petcock is a 3-position valve.
"On" and "Res" are vacuum operated and only flow fuel when the engine is turning.
"Pri" bypasses the vacuum and flows freely, and is used to prime the carbs after service or to bypass a vacuum leak issue to limp the bike back home.
There is no "off".

In regards to the "off" position, I was talking about the petcock on the fuel tank, not the frame. When I said in my first post that I turned the fuel off, I meant that I took off the seat, unbolted the tank, and used a screwdriver to turn the upper petcock off. Sorry for the confusion. Is that one not called a petcock?

[ShowBizWolf]

Ugh that one is such a pain to get to....

Welcome to the site cobo! Hope you get your bike sorted 

[RideShield]

 
I was having an intermittent fuel leak which turned out to be the float valve assembly (needle and seat with o-ring).  I went with the two of the cheapest K&L Supply Economy Carburetor Repair Kits 18-5059 that I could find. I've read where some people don't like them for various reasons but they seemed to work for me.

[Watcher]

In regards to the "off" position, I was talking about the petcock on the fuel tank, not the frame. When I said in my first post that I turned the fuel off, I meant that I took off the seat, unbolted the tank, and used a screwdriver to turn the upper petcock off. Sorry for the confusion. Is that one not called a petcock?

Yeah, its still a petcock.

Sorry, we run into so much discussion on the frame mounted one it's just assumed that's the one we're talking about every time unless the poster specifies it's the tank petcock.

Usually that one doesn't cause issues and I often wonder if most users even know it exists, lol.

[cobo10201]

I was having an intermittent fuel leak which turned out to be the float valve assembly (needle and seat with o-ring).  I went with the two of the cheapest K&L Supply Economy Carburetor Repair Kits 18-5059 that I could find. I've read where some people don't like them for various reasons but they seemed to work for me.

Thanks for your reply. I've been trying to find out which needle's work for the 07. I assumed they're all the same from at least 04, but when I do the "check if this product fits your vehicle" on eBay or Amazon it always says no.

[mr72]

I think that actual needle (the part you really need) is probably the same across all GS500s 1989-2009 plus a ton of other motorcycles with similar Mikuni carbs (dozens of other Suzukis, Kawasakis, Yamahas, etc...).

When my bike was in the shop the mechanic found one of my float needles was sticking and he replaced them both from a bin of hundreds of the same part, common as an M6 bolt.

If you hadn't already bought the o-rings, then this would be a good bet:

http://www.ebay.com/itm/SUZUKI-GZ250-99-09-GS500F-04-09-Lower-Bowl-Carburetor-Repair-Kit-K-L-18-5059-/401247549540?fits=Year%3A2007%7CMake%3ASuzuki%7CModel%3AGS500F&hash=item5d6c37b864:g:OpYAAOSw6DtYXI5W&vxp=mtr

But still, that kit has a replacement float bowl gasket, needles and seats and big deal if you have a couple of spare o-rings. Plus it looks like it comes with the vacuum port o-rings, which you may also need (I bought a bunch in bulk since they get lost easily).

$30 and you're done!

[cobo10201]

I think that actual needle (the part you really need) is probably the same across all GS500s 1989-2009 plus a ton of other motorcycles with similar Mikuni carbs (dozens of other Suzukis, Kawasakis, Yamahas, etc...).

When my bike was in the shop the mechanic found one of my float needles was sticking and he replaced them both from a bin of hundreds of the same part, common as an M6 bolt.

If you hadn't already bought the o-rings, then this would be a good bet:

http://www.ebay.com/itm/SUZUKI-GZ250-99-09-GS500F-04-09-Lower-Bowl-Carburetor-Repair-Kit-K-L-18-5059-/401247549540?fits=Year%3A2007%7CMake%3ASuzuki%7CModel%3AGS500F&hash=item5d6c37b864:g:OpYAAOSw6DtYXI5W&vxp=mtr

But still, that kit has a replacement float bowl gasket, needles and seats and big deal if you have a couple of spare o-rings. Plus it looks like it comes with the vacuum port o-rings, which you may also need (I bought a bunch in bulk since they get lost easily).

$30 and you're done!

Went ahead and bought two of those! Like you said, it doesn't hurt to have extra o-rings lol. Thanks!

[Torstein]

hope you fix your problem. my leak was caused by a bad o-ring. i replaced them all, including gaskets, and the leak stopped. i could have only replaced the 1 bad o-ring but i figured since i was in there already might as well do the rest.

[cobo10201]

hope you fix your problem. my leak was caused by a bad o-ring. i replaced them all, including gaskets, and the leak stopped. i could have only replaced the 1 bad o-ring but i figured since i was in there already might as well do the rest.

That's my thought, as well. Got it all apart, might as well change them all.

[cobo10201]

I know this thread is basically a million years old but I wanted to update it. The bike really ran fine for the past year, but about a month ago the gas leak started again and it was just constant. Only way to stop it was to turn the tank petcock off and drain the carbs. I finally got around to replacing all the o-rings and the float valve and needle. I'm 99% sure the leaks have been due to the fact that the o-rings on the float valve were essentially nonexistent with just a tiny bit of residue left behind.

Anyways, leak stopped, idle set at 1200, and a happy bike!


Sent from my iPhone using Tapatalk

[gregjet]

It sounds to me like you got sold O rings that weren't petrol resistant. By the way , DO NOT PUT CARB CLEANER near the O rings on the gs . They don't like it. If you use carb cleaner make sure all the rubber rings are out and don't put them back until ALL the cleaner has evaporated. Force dry it if necessary.
I accidentally oversprayed onto the needle/seat big O ring and watched it swell...

[cobo10201]

Thanks for letting me know. I remember reading that before so I made sure that no o-rings were present when I sprayed the carb cleaner so hopefully no more leaks... And the o-ring kit I just installed was specifically for these carbs so hopefully they're petrol resistant!

[user11235813]

@Cobo, btw that's not a breather hose coming out the bottom of the tank it's a water drain hose or fuel overflow, the tank vent is in the cap.

Ugh that one is such a pain to get to....

@SBW Ha, yeah, that used to break my back, until... I bought a long stemmed screwdriver and used decent LED torch to get some light in there, then I could see that the slot is closed on one end! Now it's easy.