> > is there a way to make your own seal with gasket paper or something?
Yes, but better not for motobecane. You can use em for the bottom gasket
and the crank-case gasket but not for the exhaust. The copper crush
rings are the only good thing to use.
BTW, when you put the nut back in, make sure you put it in straight.
Best is when the exhaust is not attached to anything when you put it on
the cilinder. I have seen many cilinders with that particular coil
completely ruined. For most the cilinder will be useless without it. So
be ware. :)