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Discussion Starter #1
Hi everyone,

It's been an age and a half since I last posted, I hope everyone is well and getting into the riding season this year. I'm doing routine stuff to my RC, and am chasing a fuel weep (too small to be considered a leak, no drips just a bit of "film") and discovered that my replacement fuel tank has a rubber plug in the overflow hole.

I got the tank from a track bike, it came with a track-type filler cap as well. I swapped over the stock fuel cap and fitted a new fuel filter and fuel pump seal, never noticed the plug in the overflow hole until now as I'm troubleshooting.

Is this a track bike thing to prevent potential fuel spilling onto the track if something happens? I'm gonna pull it to see if it changes my fuel weep, but I'm curious. The bike otherwise runs just fine, as far as I can tell.

Thanks, everyone!
 

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That might the atmosphere vent in which case I would not have it plugged. Where are you seeing the fuel? There is a gasket under the fuel cap that if it's not sealing, fuel can spill up from under the fuel cap say under breaking.
 

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Discussion Starter #3
The plug was in the atmosphere vent as you say, it's the small breather line just outside the filler hole, from there a tube runs through the tank and at the rear of the tank into the rubber vent line down to the ground. Having fuel spill up out of the tank under braking makes sense, I'll take a look at the track cap and see if maybe that's why that line was plugged. Anyway I removed it.

As for the fuel weep, I need to dig further, but I won't be back home for a couple weeks so it'll have to wait a while. The truth is I'm not even totally sure it's fuel. It doesn't look like fuel, but it does smell like fuel (maybe it just smells that way cuz it's gathered under the fuel system). It's way at the rear of the tank and underneath, where the mounting hinge is, and there's some on the top part of the rear shock and shock mounting brace as well.It's a thin film, a bit thicker than fuel is, and after months it hasn't evaporated. Nowhere around any fuel line can I find signs of a leak, I was careful to prep the tank properly for the new fuel pump seal and followed the book to the letter torqueing it into place, and everything looks bone dry. Not a drop or even any discoloration anywhere on the engine or transmission case.

I think I'm going to replace the fuel lines just to be safe, since those are original as far as I know, but as mentioned I don't think there's a leak there.

The pics show the built up film, and this is not after a ride, this is after sitting all winter after I put her into hibernation at the end of last year. That's when I discovered it, and I decided I'd dig into it this year.

Input greatly appreciated!
 

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