Hello GS500 gurus,

I rejetted my carbs over the weekend, which I thought had gone swimingly, besides tearing a stiff old fuel line from the tank which I've now replaced.

Sooo I was wondering if you could tell me what this thingy is and what to do with the end of the hose, because I've no idea and I've got fuel pouring out of my new lunchbox and am wondering if it's related?

Probably not as the bike leaks fuel when set to prime without the engine running, I don't believe the floats are stuck as they looked spotless to me, but I will pull the carbs and check.

http://s53.photobucket.com/user/Adam_duffman/media/GS500/IMG_20151017_124846%20highlight.jpg.html

http://s53.photobucket.com/user/Adam_duffman/media/GS500/IMG_20151017_142712.jpg.html


The bike will start with throttle applied, or if I increase idle with the adjuster, but fuel eventually starts pouring through the filter...

I've checked the carb breather hose, it's not causing an airlock.

Any thoughts or advice appreciated.

I believe that thing is California emissions crap.

If fuel will drip out of the air filter when the engine is running then the float height is set too high.

Looking at Baron's profile, I see he is over in the UK.... would a European GS have the CA emissions garbage? It does look like emission equipment to me though.

Baron, start by checking your float height with a clear section of tubing. Your float needles may be clean, but that doesn't necessarily mean they aren't sticking open from something else (bent tab on the float, hanging on a gasket, etc).

Thought the CA emissions cap lived somewhere else, but I'm no expert 

Check your float heights, the needle, and the o-ring that lives on the outside of the part that the needle rises into (brass thingamajigger, round, small hole in the middle).

Good luck!

PS post if you ever figure out what that piece is!

Always wondered what went on those bolt points in the frame!! .. cool!

Yea I'm UK based, got no catch can on the bike, but is likely emissions related as ran from the air box into the front of the engine, I'll post up a of where it goes later.

Ok cool, will strip carbs back down, thankfully put Allen bolt caps in so should be easy enough

Probably not causing your issue if its all adjusted right and set right.
But that sure looks even more crammed in there than the CA version of the same year GS.
Cool.
Buddha.

If it ran from engine to air box, isn't it possible it helps warm up the engine on cold starts by feeding it warmer air?

The component highlighted in your first photo is the PAIR-valve. It is STRICTLY for emissions purposes, and is not likely to have an effect on the normal operation of the engine.

It is a vacuum-operated valve which takes cleaned air from the airbox, an 'injects' it into the exhaust. The additional air will theoretically aid in the combustion of left-over hydrocarbons as they flow out through your exhaust pipes. If it doesn't actually cause additional combustion, it at least dilutes the bad air coming out of your exhaust, which will make it look better if your emissions are tested.

You should NEVER leave the petcock in PRI position. The only purpose of this is to fill the float bowls with fuel so that the engine will start. Once the bike is started, switch the petcock to ON for normal operation. LEAVE it in ON so that fuel isn't flowing into the bowls while it is sitting.

The floats are supposed to prevent overflow, so it seems to me that that is where your failure is.

What could happen if the petcock is left on PRI?

Sorry, should've been clearer on that, the bike was in Prime for only a few minutes once I'd reattached the carbs, engine off, which was enough to cause it to overflow.

Thanks for shedding light on the pair valve, not really sure what to do with it now I've got the lunchbox in, will probably try and find a way of plugging it at the valve.

I'll post a picture of where it enters the engine when I get to a computer for anyone that's interested and so it's here for reference when someone else googles it

A guy that manages our vehicles at work sold a GS to someone who kept riding it in prime despite warnings, apparently the engine filled with petrol and locked the pistons and had to be drained, not sure how true that is however...

I'd believe it. I have a GR650 engine in my garage (the GS500's older & bigger brother so to speak), and it has bent valves from the PO hydro locking the engine.

The frame-mounted petcock is vacuum-operated, JUST like the PAIR valve OP had circled in his first photo. In fact, these two valves both operate on the same vacuum line coming from the carburetors.

The frame-mounted petcock (which I will now refer to as the FRetcock, because for some reason when engineering this bike someone decided that it need TWO petcocks  ) has three positions: ON, RES, and PRI.

ON and RES differentiate between the two fuel lines coming from the tank-mounted petcock (Tetcock). The RES line takes fuel from lower in the fuel tank, whereas the ON line draws fuel from a few inches higher. The idea is, when you're tank is down to about 20%, there will be no more fuel coming from ON. The bike will start to sputter, which is apparently better than installing a fuel-light. When this happens, you're supposed to reach down with your left hand and flip the FRetcock into RES, and now you know you need to refuel sometime in the next ~30 miles (give or take).

So, ON and RES are both vacuum-operated. When a pulse of vacuum is generated by the carburetor, it produces suction on the valve in the FRetcock. This suction opens the valve ever so slightly, and draws fuel from the indicated fuel line: ON or RES. This fuel comes out the hose into the carbs, which then fills the float bowl (I haven't torn down the carbs yet, so my understanding basically stops here).

In contrast, PRI does not need vacuum to operate. It opens the valve to both ON and RES, and fuel flows in freely by gravity.

If there is a problem with your float valve, and/or you don't have a good seal on the float bowl, it's possible that gasoline will start to overflow out of the carbs, which sounds like the problem OP had.

Forgot to elaborate more on the PAIR valve.

OP, you can leave it as is; it's harmless. At the recommendation of some other posts in this form, I purchased some hyabusa blocking plates, and removed the entire valve, the line to the airbox, and the pipes injecting the air into the header. I applied the blocking plates as such:
album: https://imgur.com/a/YcDd9

https://i.imgur.com/wDECOLX.jpg

https://i.imgur.com/tbZZBEj.jpg

https://i.imgur.com/ppiGOll.jpg

I have 2 extra blocking plates since I had to buy four. OP if you're interested in acquiring from me I'd be happy to sell them to you at cost.

Quote from: Big Rich on October 22, 2015, 03:52:36 PM
I'd believe it. I have a GR650 engine in my garage (the GS500's older & bigger brother so to speak), and it has bent valves from the PO hydro locking the engine.

How do you bend a valve with hydrolock ? It will bend a rod, not a valve. Valve can bend with old gas, that can hang up a valve and that will bend it.
Cool.
Buddha.

I don't know how it happened Buddha. Low mileage bike that I flipped to a kid for profit. Couple years later his mom calls me and says "he wrecked it a while ago, and I want it gone". I go pick it up, front end is pretzeled, and gas pours out of the exhaust port when you try and start it.

Something is goobered up, and I haven't opened it up to see yet.

Yikes - OK you're hydrolocking now, that don't mean it caused bent valve.

BTW I wanted to pick your brain a wee bit ...

I want to build a GR that is nearly all stock ahead of that Fugly step up in the seat. Should have stock air box and side covers as well as battery case and electricals etc. But Behind that hump in the seat, it should essentially be flat and short.

Is there a seat available that will fit over the side covers ? Is a GS650 café aftermarket seat wide enough to fit over the GR's side covers ?
Or do I mod the seat pan ? Is it steel ? I got it lying in storage, gotta unearth it.

Cool.
Buddha.

Quote from: bertreynalds on October 22, 2015, 06:29:19 PM
Forgot to elaborate more on the PAIR valve.

OP, you can leave it as is; it's harmless. At the recommendation of some other posts in this form, I purchased some hyabusa blocking plates, and removed the entire valve, the line to the airbox, and the pipes injecting the air into the header. I applied the blocking plates as such:
album: https://imgur.com/a/YcDd9

https://i.imgur.com/wDECOLX.jpg

https://i.imgur.com/tbZZBEj.jpg

https://i.imgur.com/ppiGOll.jpg

I have 2 extra blocking plates since I had to buy four. OP if you're interested in acquiring from me I'd be happy to sell them to you at cost.

Thanks for explaining, so from what I understand, it doesn't matter if I run it for now unfiltered? I would love to get those from you please Bert, it sounds horrible left open, the pipes from the PAIR valve are crusty beyond belief as they were hidden under the fairing until I removed them a little while ago as well, image below for your cringing pleasure... In fact it's all looking a bit crusty, feel like I'm fighting a losing battle to the elements with my little GS 


http://s53.photobucket.com/user/Adam_duffman/media/GS500/IMG_20151022_181851.jpg.html

http://s53.photobucket.com/user/Adam_duffman/media/GS500/IMG_20151022_181902.jpg.html

http://s53.photobucket.com/user/Adam_duffman/media/GS500/IMG_20151022_181914.jpg.html



With regards to my little petrol problem; I adjusted the floats today, I know it's supposed to be a simple job, but I really had difficulty being able to see when the tab was resting on the needle, seemed to need a lot of adjustment, which would make sense given the amount of petrol I had running through my filter. Sooo... I've managed to reduce the petrol to a slow drip from my left carb, I'm going away in a few days, so next time I open up the carbs will be to recondition entirely with a repair kit and to replace the bowl drain screws which are f&^ked like every other bloody fastener on the carbs 

Besides the obvious problem, I took the bike for a short ride (10 miles or so) and besides being a little lumpy at idle, it all seems to work fine and cold start is significantly improved, which was always the biggest thing that annoyed me about the bike! Got my girl a little KSR Code a month or so ago which uses a GS125 engine and it starts come rain or shine, no choke, straight up to a smooth low idle, found myself jealous of the little thing!

Long story short, started bike, no fuel dripping out for good 10/15 minutes while warming up, adjusting air fuel etc. Noticed air fuel screw was actually rotating slightly while the bike was running (used phone camera to make sure I was in the right hole) Decided I'd take it for a little ride, hit some 70mph twisties to see how it was performing with the rejet and it felt great!

As I got close to home, travelling at low speed, the throttle became completely unresponsive and the bike was popping rapidly like a machine gun, pulled over and looked down and found there was fuel pouring out of the air filter. Left the bike off for 5 minutes and started up again, ragged the throttle to burn some fuel and it ran fine all the way home...

Would any of you say it is fair to conclude that this is either:

1. Float/needle sticking (Waiting until I get off holiday to order rebuild kit: http://r.ebay.com/wFG1yM)
2. Air/Fuel screw spinning whilst riding (Although my understanding is this would make it leaner and is pretty unlikely, but could cause other issues)

Can I simply unscrew the mixture screw and Loctite it? I know there's a needle and spring etc in there.