They usta sell this silica stuff that came in a tube that you squirted into the pipes at the exhaust port flange and then bolted the flange/pipe(s) up and and immediatley started the bike, so the exhaust pressure would shove the silica goop into the exhaust leaks.
Worked swell on my old '82 Virago when I switched to straight pipes. The balance tube joints leaked, and the silica plugged it up just fine.
Collect the webs the bird spider. Careful now, it's one of your most venomous spiders. When you have enough to wrap the affected areas, cover the webs with fresh buffalo dung. Start the bike and let the dung dry to a solid. Should take about 10 minutes to completely bake. Your bike is now fixed. The dung will eventually crumble and fall off but the web material will stay put, giving you a good seal.
Either do that or move yer butt to civilization, and go into an Auto Zone and ask them for 2,000 degree ceramic paste. I hear it works pretty good.
Not one's being much help here, but a better forum to ask would be the Magna forum, where they're pretty passionate about the bike. But...whether it's 200 degrees or 800 degrees you're probably best off using the highest temp sealant available to you. The combination of heat and pressure will be hard on it anyway. Could a good welder solve your problem?
Wait a minute, you live in China and can't get that silica goop stuff. Sorry, I jumped the gun again....oh woe.
Let's see, what can you use...hmmmm...do they still use packing material for water spigots in China? Maybe try that. Or some asbestos twine.
Or just saw the pipes off at the junction, and forget about it. On second thought, loud pipes get you brought up before the peoples nuisance board and you might get executed, or your organs harvested, so scratch that.
Pipe temp is HOT, so don't touch it.
Hope this helps. Can you get a nice used Chang Jiang over there? Those are SWEET!
A fiberglas muffler bandage will last about a day before a hole burns through it, unless you can wrap a piece of metal around the gap first, to keep the fiberglas from having direct contact with the exhaust gases.