Well as many of you have found, epoxy and many other glues just don't work a dam when repairing broken plastic on hard to find parts. Of course the dam plastic is old and brittle and does break easily from time to time. I have read many threads here on different solutions that work, but what gave me the best tip was someone said the plastic is in fact ABS and you could get a black ABS glue.
Well I couldn't find any black ABS glue but did have some of the standard yellow stuff laying around from plumbing repairs etc. I was repairing the left inner cowl on my GL1200I which was badly cracked, and the worst part was, this was the best of two I had. I was able to hide the worst of it with chrome covers, which of course I liked anyway
but how to repair the cracked edge???
I took pieces of my spare broken cowl, applied glue to one side of it and to the piece I was repairing, clamped them together and in an hour had a chemically bonded repair that is super strong
Now the outer edge had some holes to fill and a few more cracks there as well, solution, take some old black ABS pipe, drill some holes in it and save the filings that you create. Apply some abs glue, work in some of the drill shavings and apply a bit more glue overtop. Work it in well, as the filings soften you can shape them into the holes etc and even create material to fill larger holes. Let it dry for an hour, and you can file it, sand it and get it back to a fairly nice finish.......it took some time but the result was worth it. I applied Mothers Black is Back to the finish and it is very hard to tell from the original