carb issue--gas leaking out the drain


5 replies to this topic
  • deblaw2232

Posted March 02, 2008 - 06:13 PM

#1

Got a carb issue. When I turn the gas valve on, after about 10 seconds, gas leaks out the drain line at the bottom of the bike. It is the same line that hooks on the bottom of the carb near the bowl and has the brass bolt going into the carb horizontally so you can drain the bowl.

I checked that bolt, and it was closed. It appears to function properly. If I open it, it will drain gas out. If I close it, it stops the flow.

I tried cleaning the carb, same result. In the cleaning process, I checked the floats, and they don't appear stuck.

I didn't have this problem a couple months ago--the last time I rode. It appears to have developed while the bike has been in the garage.

Any ideas would be appreciated!

  • new2blu

Posted March 02, 2008 - 06:55 PM

#2

There could be a few things that could cause this problem:
1. a small piece of dirt on the float needle causing it not to cut off fuel supply

2. float level could be too high causing an overflow

3. I have heard of some older plastic floats that can have gas attack the plastic and have some fuel go inside the float--making it sink too much which would allow too high fuel level

4. I have seen a not level (installed crooked) carb which I believe caused an overflow

5. one more thing--check the rubber end of the float needle to see if there is a groove in it--a new one should be shaped like a perfect "V"
Hope this helps

  • deblaw2232

Posted March 02, 2008 - 07:23 PM

#3

Will give it a try. I forgot to post, it's a 2003 WR 450.

  • matt4x4

Posted March 03, 2008 - 06:06 AM

#4

it's definitely something with your needle valve/float assembly.
since you turn the gas on and after a bit of time, gas starts to come out continually, it's definitely one of the two listed things.

Needle valve or seat is worn, dirty, stuck (possibly varnish buildup)

Float is stuck open, float has taken on gas and is now sitting lower, keeping valve open longer, float arm is bent.

Don't just bend the float arm to "fix" the problem, please find the problem and fix it right since bending the float arm will mess up your level in the bowl and the level in the bowl needs to be correct for the carb to function properly.

For times like this, I wish they made a clear bowl (just for troubleshooting, not as a permanent bowl) to make troubleshooting easier, having a clear bowl will let you see it all in action and adjust your bowl fuel level perfectly.

  • deblaw2232

Posted March 09, 2008 - 03:03 PM

#5

Well, how about this--turns out the idle adjust knob was way too far in, holding the throttle open. Of course I don't figure this out until I've taken the carb off, apart, etc and start messing around with it because I don't find gas in the floats, the floats adjusted wrong, gunk in the carb, or anything wrong with the needle, etc.

  • matt4x4

Posted March 10, 2008 - 05:56 AM

#6

having the throttle held open by the throttle screw does not make the carb leak gas in an off state, the carb will only leak gas when the motor is off if your needle valve is stuck open due to the above mentioned conditions (needle valve = the valve that controls gas flow entering the carb bowl - controlled through floats and fuel level in bowl.)

The throttle only controls the height of the needle in the main valve, it does NOT turn on a gas spigot, it does nothing else other than lift a needle which in turn allows a variable amount of gas to move up past that needle to mix with the air being sucked through the carb on it's way to the engine's combustion chamber. This only happens when the bike is running, when the bike is off, lifting the needle up as high as it will go does nothing.

The accelerator pump can squirt gas while the bike is off because it gets controlled by a diaphragm that can pressurize the gas without needing airflow, however, continuous throttle movement is needed to keep this gas squirting since the throttle also controls a pushrod that moves the diaphragm.

More than likely, once you removed the carb, the culprit dirt or whatever had long washed off the needle jet and everything went back to working condition before you even tore into it. It's usually just one grain of sand so small that hte eye doesn't see it that causes this condition, however, the idle adjust knob does not cause gas to leak out the overflow.




 
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