Fuel Leaking from Airbox drain hose...

[phlooke]

Hi all,

I am hoping someone here will be able to throw some light on this for me.

I have searched previoius threads but cannot find an exact match for this problem.

My GS is leaking fuel from the airbox breather hose. It just started recently out of the blue !?
Initially I thought it was faulty float valves + seal's...I couldn't locate a new set so when the opportunity arose to buy some carbs from a dismembered GS I bought them.
I stuck the replacement carbs on and to my dismay I have the same problem  :dunno:

Petrol seems to be filling into the float chambers and then continually flowing; it overflows through into the air filter housing - the airbox - and then trickles out the drain hose.

After fitting these replacement carbs, reseating all hoses and petrol tank I set the main fuel tap under the tank to the 'ON' position. I hear the float bowls fill and the bike starts and runs.

I then leave it standing for about 45-60 mis and the petrol leak begins ??


It seems to be a bit odd that two sets of carbs should have the exact same problemso during my very basic fault finding process I turned the tap 1/4 of a turn round from the 'ON' position; the fuel leak stopped. I left the bike overnight.
Next morning (today - Sun 31 oct) I tried to start the bike...it wouldnt start. I set the tap back to the 'ON' position and the bike started after a couple of tries, it ran OK so I switched off, set the fuel tap back to 1/4 turn on from 'ON' and the bike started but wouldnt pull away in gear...it just died.

What is this extra position on the fuel tap for? ....and can anyone hazard a guess as to what is wrong or what I should try next ?

Sorry for the long post. Tried to get the whole story in.
This is driving me mad
Thanks in advance for any help.

Scott.

[phlooke]

Hi again,
trawling through old posts found this post ..http://www.gstwins.com/forum/viewtopic.php?p=105387&highlight=#105387 with a diagram showing the remote fuel tap positions.....

Mine has always been pointing up i.e. the same as position 3. in PRIME. COuld this be why fule continually flows from tank to carbs to Airbox ??

I have set my remote tap to position 1. i.e. ON and will monitor the 'leak' BTW I have set the main fule tap (under the tank) to the ON position.

If I have no leak I'll try to start later and report back.

Fingers crossed.

Scott.

[scratch]

Welcome, and good job on finding a potential reason for your problem! Hope it's as simple as selecting 'On' versus 'Prime'.

[phlooke]

Hope so too...I have been checking it periodically all afternoon and there is no sign of any fuel leaking.

Fingers crossed...still  

[ponchopirate]

If you left it on prime it will bypass the vacuum and just let gravity keep pouring gas into your carbs making the bike difficult to start and potentially send gas leaking out of various spots.  You only use prime for a few seconds if you've drained the gas from your float bowls (say after taking your carbs apart) to fill them back up and get the bike started, after that just leave it in the "on" position (down).

[phlooke]

Right then a quick update...

Since I moved the remote fuel tap into the 'ON' position as opposed to 'PRIME' the leak has stopped and the bike started 1st time this morning  

Thanks for the reply's.....and thanks to everyone who has posted reply's to other fuel related post's, they were invaluable help to me.

I am such a "pratt" for leaving it in 'PRIME'  


Scott.

[jawntybull]

Hi all,
This problem started for me yesterday - fuel dripping slowly from the airbox breather hose. From reading other posts it could be the vacuum fuel valve of the carbys needing a clean (stuck float or valve). I'm trying to decide where to start, and my logic is:

- if the vacuum valve was working properly (it's in the normal ON position) no fuel would make it into the carbys anyway when the bike is standing still. So it has to be the vacuum valve. If it was the float or valve in the carbys, this would not matter as the vacuum valve should stop the fuel flow anyway.

Am I right? If so I should replace the vacuum valve before pulling the carbys out.

Two other symptoms that may help - the bike is hard to start (probably flooded carbys), and at idle, when you stop at the lights, it idles ok for 10 secs or so then starts to slow down, right down to less than 1000rpm. Maybe the fuel leak is starting to make the mixture too rich when sitting at the lights??

And a final piece in the puzzle - I filled up yesterday just before the problem started, and had been on reserve for a little while before filling up. Maybe some crud was sitting in the bottom of the tank and it's now stuck in a valve?

[jawntybull]

For anyone with a similar issue - fixed it today without doing much. I figured the vacuum valve had to have some gunk in it, so I rode along whilst turning the tap from ON to RESERVE and back again a few times. Whatever it was, it's gone now (probably blocking up my carby now though) - at least the bike isn't leaking fuel any more

[Smokebombb]

I had a similar problem with my 2004 gs500f.  My bike was running fine, but I hadn't cleaned the carbs in 6 years.  So I take the carbs out, do a thorough cleaning, and put the bike back together.  I am sure I connected all the hoses back correctly.  The back ran fine for 30 minutes on the freeway.  As soon as I got off the freeway the bike died.  It started up again sluggishly and puttered until I got home another 5 minutes.

Gas was dripping from between the carbs somewhere and gas was entering the air filter housing and leaking down the air box drain tube down by my right foot.

To fix this all I did was turn the gas line off at the tank-mounted petcock, and drain the float bowls by undoing the drain screw at the bottom of each bowl.  Once I turned the gas line back on, I started the bike as usual, and went for an hour long test ride.  So far so good.

My guess is the floats were stuck, maybe by some sediment coming through the gas hoses, and causing gas to overflow the bowls.  Draining the float bowls may have dislodged whatever was keeping the floats from moving freely.

[jacob_ns]

Ensure you don't have fuel in the cylinders now or you'll risk hydrolocking the engine.

[ramennoodles]

+1.  When I had a fuel leak there was a lot of fuel that drained through and made it into the crankcase.  A lot of fuel was in there with the oil.

Ensure you don't have fuel in the cylinders now or you'll risk hydrolocking the engine.

[ben2go]

You need to fix the float that is sticking and causing the engine to flood.A properly tuned set of carbs will not flood when sitting.If oil was dripping from the air box drain,There is most likely gas in the oil.Gas in oil can cause bearings to spin.if the oil thins out enough.PRI or prime position is for starting the bike.After it's running the petcock should be set to the ON position.