Yamaha Aerox 50 - Exhaust problems.

[Baxendale]

Hi guys, just bought a new pipe for my Yamaha Aerox YQ50, tried bolting it on the other night and the small flange pipe at the end of the exhaust (manifold end) that slots into the cylinder doesn't actually fit into the cylinder manifold hole (flange pipe is round - manifold isn't completly round). Therefore I took a hacksaw to the pipe and removed the small flange pipe to make it flat fitting, so now it fits fine but after say 10 miles of riding it (depending on how hot the exhaust gets) the exhaust gasket sealant just burns away and the exhaust starts blowing, also I have tried using a paper gasket and this also just burns away but on my other exhaust it doesn't? Something tells me the manifold of the exhaust is no longer completely flat, it looks a little out but this might just be me. Is there any way to get it flat? I've tried a file & wire brush and can't seem to level it out (if it is this)

Thanks

[rezzin]

Buy it new? Is it for your specific model. Where from? You filled in where you sawed yes?