OKGuys. the Thunder Tigre GP-42 doesn't have a nose bearing, and I'm not sure about the main. It is a bushed crank, not a ball beraring one. Given that, get some good cleaner and clean your plane after every couple flights and don't worry about it. What you are seeing is blow by out the front bushing. Not much you can do about it. short of some serious machine work.

Here is a photo of the crank case http://www3.towerhobbies.com/cgi-bin...LXAJKM&P=Z

Here is the total parts breakdown http://www3.towerhobbies.com/cgi-bin...RG1041&P=Z

And here is the manual. Notice that there are no bearings to be replaced on the break down drawing.
http://manuals.hobbico.com/ttr/gp-series-manual.pdf

Don

PS now I'm sure about the main being bushed also.