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Carburetor Leaking Fuel Out Drain Tubes?

64K views 16 replies 6 participants last post by  Chris Freebairn 
#1 ·
Finished my ride today and loaded the 2003 Grizzly on the trailer. I soon noticed fuel coming out of carburetor drain tube. The fuel **** was off but it would not stop. I moved the end of the hose to a point above the fuel tank and in a minute fuel started coming out of another drain hose that connects to the carb a little higher up. I think that hose is the "Vacuum chamber breather hose" but am not sure. I raised the second tube as high as I could but eventually it starting coming out again. This leads me to a few questions:

1. Can I assume the fuel **** valve is broken and needs to be replaced?
2. Why did the carb float not stop the fuel from flowing?
3. By raising the end of the hoses to a point above the carb did I force gas to leak into the cylinder or engine?
 
#3 ·
Once fuel line was shut off it should have stopped leaking if shut off was working properly (very soon). Sounds also like needle/seat issue. Pretty easy fix. I've always replaced those parts when encountering this issue (small price) but someone on here said you can fix the problem most of the time by "cleaning" needle with fine steel wool. Best of luck.
 
#5 ·
The needle and seat is in the carburator... fuel shut off petcock is under tank, before carb. totally unrelated issues. That's the bad news. Good news is that neither problem is typically difficult to fix. And whenever I've changed fuel shut offs (never on a griz for the record) I've had to drain but never remove the tank.
 
#7 ·
First of all I think there is more fuel in your carb than you realize. It sounds like your float is stuck. If you have someone help you you can hold the rear brake and lift the front of the Griz in the wheelie position. Then let the front wheels drop. This may jar the float loose.
 
#8 ·
Thanks Starsky but it leaked at least 2 gallons so that rules out the carb only. Good idea on shaking the float loose. If it happens again I will try that technique. I think I will take this opportunity to take the carb out and give it a good cleaning and replace any worn parts. Better now than deep in the woods.
 
#9 ·
I would have to agree, I don't think the carb holds 2 gallons of fuel. Good luck and let us know what you find out.
 
#10 ·
I hate when guys ask good questions and then never come back to explain what the result was so here goes.

I found a small piece of black rubber stuck in the float valve. The needle could not seat properly. It was part of the shutoff valve that broke free and floated down stream until it got stuck. The shutoff valve was shot but the needle and seat were fine once the piece was removed. I have since added a fuel line filter between the shutoff valve and the carb. I do not understand why a filter is not a stock part on the Yamaha ATVs.

Thanks all for your help.
 
#12 ·
Glad to hear it wasn't a big deal after all. Any idea how the fuel valve came apart? This is some very good info, thanks for posting the result.
 
#13 ·
Thanks Tinpusher, glad you got back to us. I hate it too when you never find out the reason(s)..........Irv
 
#14 ·
Just had this problem on a ~ 2010 grizzly 450 here in Aus. Fuel **** not working, evident by no reserve fuel available, fuel shut off not functioning & tank drained via the carburetor. Fuel draining continuously from the water trap/flooding overflow hose at bottom of the carby & not able to be stopped with the fuel ****. Emptied a tank & a half of fuel with minimal bike usage before I realised something was wrong becasue of a fuel smell coming into our house when the bike was partkedf upwind of the window facing the TV!

Bike ran OK while there was fuel, tho it was missing a bit in reverse.

Saw this post on first Google search & went to work. Air filter box full of fuel up to the carby air hose, so presumably fuel would have drained into the engine too.

Fuel **** inner gasket eroded between the reserve & shutoff ports so when the **** was in the off positions fuel was able to run thru to the carby, & in the on position it was able to run from the reserve port, hence no reserve available when I ran out of gas in the normal position. Sounds complex but when u pull it apart it is readily understood.

No sign of debris under the float chamber needle but gunk round the bottom of flat chamber. Cleaned it out, put back the float cover & closed the water valve then filled float chamber with fuel via the carby fuel line. Initially fuel ran out the carby's bottom water drain/overflow line because I had overfilled the float chamber ( it flows thru a small diameter copper pipe that projects upwards into the float chamber & removes the excess fuel when u flood ur carby), but then it stopped. Opening the water drain screw allowed more fuel to flow from the same pipe, as it would when you drain water from the float chamber.

This tells me the float valve or needle valve is functioning properly when the chamber is full of fuel, ie nothing running out the drain pipe when it shouldn't.

Haven't got the parts for the fuel **** yet, but anticipating asll will be well when I reassemble. Only had one or 2 bolts screws dropped into the motor, but recovered all, and intrigued by the use of carefully zip tied chux in place of an obviously more expensive air filter. When I first opened it I thought it was an oil filled air filter, but of course that was petrol held in the air filter box by the plug in the end of the water tell tube.

Not sure why they plug those drain pipes, better to just have the pipe open so whatever can drain without human intervention. The one on the shift lever is another one very easy to miss & can back up the water into the very area where it is draining .. not ideal design IMHO.
 
#15 ·
Aussie with same problem

Fuel **** malfunction is a sign that a piece of the rubber gasket inside it has detached, allowing fuel to run to the carby when the **** is OFF, and also probably allowing the reserve fuel to run out when the **** is in the ON position, leaving u with no reserve when u run out of gas.

Fuel filters are inside the tank - one on normal line the other on the reserve line, part of the stop **** assembly, but to deal with this problem an inline filter is required between the problematic stop **** gasket i & the carby.

In my case fuel tank was emptying faster than it shld and we smelled petrol & noted fuel running from the bottom carby drain hose. That hose has a screw near its connection to the carby which is used to drain water from the carby - its heavier than fuelk so sits in ur carby bottom. If that screw is closed (normal position) fuel can only come from that drain pipe if it is higher in the carby than normal. There's a thin copper or brass pipe that projects upwards into the float chamber, normal fuel level is below the top of the pipe, flooded fuel level is above the top of the thin tube & runs out the drain pipe. A flooded carby can often be restarted after a short wait to allow the float chamber to drain to its normal level.

I tried to kink the drain hose but next morning the fuel tank was dry. Disassembly showed the air filter compartment was full of fuel up to the air intake to the carby. I assume some wld have gone into the motor as well as the inlety is at the same height as the air filter inlet.

So air filter compartment removed, fuel removed filter dried, and stop **** dismantled after removal of fuel tank. Disassembly showed the rubber gasket that control fuel flow/direction was broken, just a small piece missing, but enough to allow fuel to run where it is not supposed to. Its a clever little system how the stop **** works and it will make u smile when u see how that little bit of deterioration produces the malfunction we are talking abt on this thread.

Carby removed (left choke & throttle linkages attached) & bottom 4 screws removed to get to the float chamber.

There was nothing blocking the float valve but gunk on the carby bottom plate (where the drain is at the bottom) so cleaned it all out & replaced. Put fuel into the carby float chamber thru the hose from tank to carb & observed it running out the drain pipe then stopped. Opened the water drain screw & remaining float fuel ran out.

This indicates all is now well with the float & float chamber valve; the initial run out from the pipe was because I over filled the float chamber with the fuel I poured in.

Not sure that float valve is a needle valve, it is short & fat & has a rubber tip, looks like a stubby pencil. Needle valve is higher up in the carb and accessible thru plastic cap on top of carb. It has a long spring & a black rubber diaphram that under vacuum lifts or drops the needle valve & assembly within the carb on throttle action.

Waiting for the stop **** part to complete reassembly.
 
#16 ·
Hmm, I decided that the fuel **** was not going to release more rubber bits and that I wld reassemble without new parts. To prevent a time costly further disassembly I located a fuel filter from a discarded ATV at local car dump, cleaned it with fresh petrol & put it in line between the fuel **** & carby.

Initially took a while for the filter to fill with fuel - helped it along by wobbling the bike side to side by hand. I observed fuel coming from the bottom carby drain pipe & thought I still had a problem in the float chamber, but after I opened the water drain screw a couple times it seemed to resolve so no fuel coming from that drain pipe.

Also checked for fuel to the carby by removing the fuel line at the carby - plenty.

I then tried unsuccessfully to start the bike using the pull chord as I have no battery atm. Removed the plug to check for wetness & for spark, thinking that fuel must have gone into the combustion chamber as it is at same level as the air filter canister which had been full of fuel. Attached plug to lead, sat it on the exhaust pipe & pulled her over a few time & spark was present. First pull delivered a spray - like a sneeze of fuel from the plug hole, showing that there was excess fuel in the chamber. Probably shld hv done that before trying to start it.

Compression on my starting attempts was not notably higher than normal, which is quite stiff. Only a singly spray of fuel came out, nothing on subsequent pulls.

Checked the oil and it appears normal, ie no sign of fuel in the oil as wld occur if it had leaked down past the rings. No flames from the exhaust either as it is well cold by now so ignition wld not occur there.

Cant imagine I have bent anything as can occur with hydrolock because with no battery & only my arm turning it over it is hard to imagine me bending a conrod or damaging other metal parts.

Still wont start tho. This morning Ive taken the plug out a left it out for a while hoping that may further clear any liquid in the combustion chamber, tho I think turning it over with the plug out shld have removed it all.

Ant thought anyone????
 
#17 ·
The fuel stop **** saga continues.

My oil smells like fuel and looks thin, tho there does not appear to be greater volume of oil than before so wonder where it went? Further reading found threads mentioning this as part of fuel **** failure problem. Looks like have to drain it & replace oil & filter.

Glad it didnt start, tho maybe thin oil wldnt do too much damage over a short running time, but still wondering why it wldnt start.
 
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