New member here, just bought an 01 YZ 125 yesterday. I'm new to riding but have experience working on 2 stroke engines so hopefully this won't be too much of a fix, but I need some help. The bike was running fine all day yesterday and this morning until I took a break to start cleaning the plastics. Then i noticed that fuel was leaking out of the bottom most vent tube on the carb. When I turn the petcock to the off position, there is no leakage at all. The fuel only leaks when it is in the open position and comes out in a solid stream, not just little drops. I am under the impression that what I have here is a stuck or leaky float. I gave it a few taps with the end of a screwdriver and it seemed to decrease the amount of fuel dripping out, but it still drips pretty good. Is my best bet here to pull the carb off and take it apart? What tests can I do once I have the carb off to try to identify the problem? The bike still runs fine (doesn't bog down or behave strange), just leaks a good amount of fuel when i am not riding it and the petcock is in the open position. I don't have a carb rebuild kit right now or a manual for that matter and was hoping to have this fixed up tonight so I would appreciate any responses or pointers. Also, there seems to be a pretty good amount of "spooge" built up in the Powercore 2 silencer that spits out when i ride. Is this normal or are the jets set too lean?

If anyone knows of any sites that have a pdf of a service manual, please let me know too. Thanks a lot.

Edited by eric-cartman, 20 February 2012 - 04:40 PM.

is it leaking from the hose on the bowl?

riding cures ALL, on 20 February 2012 - 02:08 PM, said:

its leaking from the hose

have you tried turning the bowl drain screw? it could have possible vibrated and loosened up. i would highly suggest getting a manual

there's free pdf manuals on http://www.yamahaown...ook.com.au/?r=0

thanks.. got the manual downloaded. when this started to happen, i closed the petcock off and ran the remaining fuel out of the carb. put it away in the garage and just went back out there. turned the petcock on, started it up, and it did not leak any fuel. so i am assuming it was just a stuck float. i will take a closer look tomorrow but i think the problem is solved. i will probably get a carb kit and rebuild it anyway though. now, about the spooge, there are drops of oil on my swing arm as well as my rear brake assembly. is that normal or excessive? should i take the powercore 2 off and clean it out and repack it? maybe the guy that owned it previously was running a really rich mix and the spooge in the silencer is just left over from him? what do you think?

The float inlet needle is stuck..either from debris or gummy residue. Sometimes you can tap on the carb bowl and they will unstick....but you may need to drop the bowl and do a thorough cleaning.

Some carbs have an o-ring that seals the float seat to the carb body. They can get old and shrink allowing fuel to run past the outside of the float seat even if the float needle is shutting the fuel flow off.

Blackwoodz, on 20 February 2012 - 03:57 PM, said:

x2 I had this same problem on my 04, I replaced the float needle because the little hook was missing. I put it back together and the leak was gone. A lot of the older yz's have that problem.

MX Tuner, on 21 February 2012 - 08:23 AM, said:

That's where I'd put my money.

We had a leaky carb, and it took awhile to figure out the cause was the wrinkled and cracked o-ring that sits under the float seat.
You have to buy an entire needle assembly to get the o-ring, but it fixes the leak.

The bike? A 2001 YZ125.