Trouble starting, and fuel leak from air box drain hose

[Purtsam]

Hello everyone!

So I've had my GS since august and it has been running very nicely and starting on the first try. Now I'm having lots of trouble to even start the bike, so I would hope someone could give some advice to what is wrong.

Recently the bike is giving me a lot of trouble. Im currently running with carburetor fluid (isopropyl alcohol) which helps mitigate condensation and icing of the carbs, as it is a bit below freezing at the moment (-2º). It has been running just fine in the could previously. The bike now has lots of trouble starting now and will sometimes start with the help of cold start spray, but I have to keep in high revs all the time, otherwise it will die, and be unable to start at all (revs around 4-5K, if it dips under it will die no matter how much throttle I give). Also when I'm trying to start it, a lot of fuel leaks from the air box drain hose, its not dripping, its like a small steady stream. Think of a faucet being closed almost to the point of dripping. This seems like a rather large amount and is concerning to me. Could this leak be from using such a long time to start it, or is it a problem with the carburetor itself?

As of right now the bike is impossible to operate as revs has to be kept above 4K, otherwise it will die. It acts as if it never gets hot, but I had it running a decent period of time at one try at starting it, and it still died when it tried to let down on the revs. After that it was impossible to start even though the engine was nice and hot.

Maybe fuel mixture is too rich?
Carburetor disassembly and clean?

Please advice on tips and possible solutions

Thank you!

[mr72]

I think the reason fuel is coming out the drain hose is because it's flooded. It's flooded because it is not starting, but it continues to dump fuel.

It could just be the float needle valves (one of them anyway) are stuck open causing too much fuel and flooding. In any case fuel coming out the airbox drain hose is certainly cause for investigating the float needle valves and setting float height. If you haven't done it already and recently, it's probably also a good time to go through the carbs and replace all of the o-rings, replace the intake boot o-rings, and in general give the carbs a tune up, as outlined in my blog.

It could also be that one or the other of the pilot air inlets are clogged or blocked, causing no air to flow over the pilot jet which would cause it to not run below 4K rpm. But you'll find and clean that in the process of freshening the carbs. Same for other likely causes, maybe slide(s) sticking open for some reason, etc. Basically diagnosing is kind of a waste of time, I'd spend that time doing the carb refresh procedure and eliminate all causes of vacuum leaks first.

BTW there are other things to check if the bike will idle and run at low rpms fine until it's hot, then quits running at low revs only when it gets hot. If that's the case, then I have some other suggestions to check (valve clearances, compression). But if it won't run under 4K rpm when stone cold then the problem is most likely carbs, could be a dozen things, all solved by refreshing the carbs with $30 worth of parts and 2-3 hours work.

[the_63]

My bike has been running really badly lately. I refused to look at the carbs because I'm putting a new exhaust on soon and will have to re-jet to compensate, but I finally gave in and removed the carbs. the float bowls are full of brown chalky crap. I only cleaned and rebuilt them 10 months and and barely rode. probably what caused it.

But my bike was doing the same things was, going to give the carbs a clean and see how that does

Chris

[lukinhasb]

I had the exact same problem in mine.

In my case, it was the inner rubber of the fuel selector valve (pri-on-res) that gets old and dried out and allows the gas to go through even though there is no vacuum of the engine running to open it.

In my case, I adapted an electrovalve 5/16 (8mm), replacing the fuel selector valve altogether, it works by allowing liquids do pass when it gets electrical current going through it, so you just remove the fuel valve, plug the in and out connections in the electrovalve instead and connect the electrovalve terminals to the bike electrical system, so it gets current when on.

Works like a charm. It stopped leaking gas through the air box drain.

[The Buddha]

My bike has been running really badly lately. I refused to look at the carbs because I'm putting a new exhaust on soon and will have to re-jet to compensate, but I finally gave in and removed the carbs. the float bowls are full of brown chalky crap. I only cleaned and rebuilt them 10 months and and barely rode. probably what caused it.

But my bike was doing the same things was, going to give the carbs a clean and see how that does

Chris

Chalky crap = your carbs have lost that "sheen" they had. The new fuel is freaking murder on them. But also an aggressive alkaline cleaner could have done the damage too, then the alcohol and oxygen in the gas finishes the job.
Cool.
Buddha.

[the_63]

My bike has been running really badly lately. I refused to look at the carbs because I'm putting a new exhaust on soon and will have to re-jet to compensate, but I finally gave in and removed the carbs. the float bowls are full of brown chalky crap. I only cleaned and rebuilt them 10 months and and barely rode. probably what caused it.

But my bike was doing the same things was, going to give the carbs a clean and see how that does

Chris

So my carbs are dead?

Chris


Chalky crap = your carbs have lost that "sheen" they had. The new fuel is freaking murder on them. But also an aggressive alkaline cleaner could have done the damage too, then the alcohol and oxygen in the gas finishes the job.
Cool.
Buddha.

[The Buddha]

You should see less and less chalky crap and that = your bike isn't dead.
If you see more and more, that = dead. The hope is that you have had it from an isolated spot and it just accumulated. If its the whole carb, or most of it its pretty much adios.
Cool.
Buddha.

[gregjet]

What Buddah said . Plus if you can use other than fuel with ethanol in it do so. Lots of crap around about the evils of alkie in the fuel, most of it rubbish, BUT for carbs with brass in  ( jets, floats, jet holders, emulsion tubes , needles etc) and unsuitable polymer fuel lines, ethanol actually reacts with them.
Modern cars and bikes don't care, but anything with brass and older fuel lines often do. They have steel lines, steel injectors and suitable polymers in seals, lines etc.

[Numewsm]

My 2004 500f has just dumped most of the fuel tank through the carbs into the cylinders and crankcase 
i had trouble starting it for the previous week, daily commute, and it would puff white smoke out the exhaust till it warmed up slightly after 2 minutes.
I was then off work sick so the bike was untouched for 5 days, hence i came back to it being hydro-locked with fuel.   
Bike was immediately drained of fuel and oil, 5Lts alone out of the crankcase!! I flushed the crankcase through with more oil and drained it again.  Drained the cylinders and put some oil in through the sparkplug holes.  Airbox was flooded with petrol also. 
Currently sat forlornly stripped apart with all possible holes open drying out the petrol.
I've got my carb rebuild kit x 2.  New allen key bolts for top and bottom.
It has a k&N airfilter in the stock airbox.
I'm suspecting its the float valves/seats to be the issue as the petcock tested fine.
Hopefully this will solve my issue at least.
I did put through a carb cleaner in the tank two weeks ago, so that may have dislodged dirt in the tank and f@#ked it up completely as it has had a minor fuel leak before, but i put that down to the fuel pipes from the tank leaking air as when i checked them they fell apart!! 

[Purtsam]

Hello again!

Sorry for not getting back sooner, but I have been very busy with a new job. So as advised I took a look at the carbs. I have been working on mopeds before so not completely new to me. So when I took the bowls off the carbs I inspected the valve seat, and it was completely loose. I could just take it out. I think the o ring securing the valve seat got old and shrunk.

I also had a look at the valve clearances while I had the tank off. Spent an entire evening getting a rounded bolt off from the valve cover, it was reaaally tight. Had to get in there with a pipe wrench in the end. All valves are unfortunately too tight, but the buckets can still rotate. It was really hard to get the shims out without the valve bucket tool, but after some practice I got them all out to check the sizes.

I have ordered a valve bucket tool, 4 new shims, 2x carb rebuild kits, and the valve cover bolt here at a dealership in town. Couldn't find any online, but the part was much cheaper than expected, so no harm done.

Hopefully when I get all the parts installed and get the carbs cleaned good, it will run perfectly again. Will update with more once I'm done 

[Purtsam]

Got the new shims and rebuild kit, and installed them. Bike runs great and starts right up every time, even though it's just about freezing. Now the thing is that the bike will not idle without choke. I thought this was because it was quite cold here, but the engine is too hot to keep a hand on, so I think it is sufficiently warm.

It will only run without choke, if I give it some throttle, and as soon as i let go of the throttle it just slowly dies. I was thinking about increasing the idle screw, but it has been working fine before, and it dosen't seem like the actual cause of the problem either. More like symptom treating rather than disease treating.

Any possible causes for this problem? I was thinking clogged idle jets, but i just cleaned the carbs.

[The Buddha]

Shims - did you get those breakaway model shims - cos those are junk, they tend to break and destroy your motor.
The idling problem - unrelated to that shim BTW is possibly that your idle screw is too far out. Or air screws too far in.
Did you synch the carbs when it was apart ? Then you need to screw the air screw (throttle stop screw) in a bit more.
Air screws are supposed to be 3 turns out, but that's just a starting point. A bit more or less as needed.
Cool.
Buddha.

[Purtsam]

Actually the shims came from a local dealership, as it turned out the first set of feeler gauges which I borrowed were really inaccurate, as the feelers were a little bit rusty and the clearances were all over the place. Ended up buying a new feeler gauge for myself and the shims from the dealership, all looking good now.

Didn't touch the air mix screw or the idle screw during rebuild as i did not want to mess up any previous adjustment, but I guess I'll have to now. Im going to clean the carbs, clean out the pilot jet etc. and reset the air mix screws 3 turns out, and try to fine tune afterwards. Also I did not synch the carbs.

You reckon that will solve it maybe, with adjustment of idle screw for ±1200 RPM idle?