2003/2005 FSE 450cc oil leaking problem

[Ladse]

Hi! In advance, sorry about my english.

I have a problem with my 2003 GASGAS FSE 450, with a 2005 engine. The bike leaks oil from the place where frame and swing are attached. It seems like it's draining from the oil tank trough the frame. I draw a picture about it.?

What I have thought is that piston might be loose and cause pressure. And the pressure comes out of the vent which is located under the oil tank cap. There has been also some oil leaks near by that vent. But if this is the case, why the engine hasn't lost any power and it runs so well? I'm going to change oil and see what happens, but that shouldn't affect on that. Thanks for the help.

[Vinny]

Looks like your hose coming out of the crankcase has been put to the highest possible position. It will still throw out oil from there . It's usually routed to your air cleaner. I made mine go from the crankcase , above the engine ( under the fuel tank) and then back to the air box. Oil still comes out but it lubricates my chain in the process. Wash after riding. Took a while to get used to it.