Need help identifying black debris on fuel tank

[neeper]

I'm not sure if I'm posting this in the right section... I took my Marder out last weekend and noticed black powder like debris on the fuel tank and chassis. The debris is only in front of the gear carrier side/clutch so 'm not sure if it's from the clutch, exhaust or the motor. I don't see any oil leaks near the head gasket or exhaust. Do you guys know what this could be? The motor is a Zenoah G260RC and the pipe is a Jetpro if that helps.

 

[evssv]

clutch dust imo...and poss combination of all of it....bearing grease/oil ect...

 

[machine head]

I got the same thing in my tank, dirty gas at the pump. Filter it before you fill your tank and get a better filter than the clunk inside the tank Machine Head

 

[neeper]

Oh this debris is on the outside of the tank, not inside