head tube leakage?

ok i have a 99 yz400f and i noticed that there was a little bit of oil around the frame right in front of the filler hole. i don't spill the oil to often and when i do it gets wiped right away. it almost looks like a little crack there or something. could it be cracked? its a small amount but i notice its a little wet in that area after a ride. any one else have this prob?

Haven't run into that myself, but I've seen it on other bikes that carry oil in the frame. Here's how I would find out for sure. You will need a regulated, or hand pumped supply of compressed air. Don't use more than 15psi for this.

Drain the oil. Disconnect the two oil lines at the bottom of the oil tank and replace them with a loop of hose so that the two fittings are hooked together, and the engine's disconnected. Remove the vent tube from the frame. With the oil cap in place, pump 5-10 psi of air into the frame through the vent, and brush soapy water over the suspect area. Bubbles are bad.

If it's really cracked, find a competent welder and get it fixed while it's small.

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