First, drill a small hole at the end of the crack, this relieves the stress and will keep it from cracking farther.
You have 2 options, the "Frankenstein" repair, drill holes on each side of the crack, and use zip ties to pull it together,makes it look like a big stitched up scar, hench the name. Or get a plastic repair kit from Dennis Kirk or other suppliers, and give that a try. I once repaired a broken lower front fender on my Wolverine with a hot air plastic welder, you need the proper type Polypropolene rod to make a weld that sticks, easy, since mine was white. It has held together for the last 10 years, so that may be what you want to look into. A vendor called "Plasti-weld" makes sticks that go into a hot glue gun and do a pretty good job,and comes in several different colors.
Since I ride in really rough areas, I have torn and cracked fenders many times. I would be broke if I bought new fenders every time I split a fender.
I have made several successful repairs on Honda (red) plastic fenders over the years using a more refined version of the "Frankenstein" repair.
Using the plastic from a small red gas can, which are cheap at Walmart. You can use a used can, but sometimes the plastic gets brittle from the gasoline.
You can even cut corner pieces from the can to match the corners/curves of the fenders.
once you have cut pieces big enough to fit underneath the cracked area of the plastic fender, (leaving about 1/2 inch to 1 inch on either side of the crack) drill a pilot hole through the fender and the patch to hold all the pieces in place on either side of the crack and run a single zip tie through the holes. once you have it held in place by the single zip ties, you can drill several holes to run zip ties throughout the patched area. Dont be afraid to make several of them
NOW....cut the zip ties you used to hold it in place. Using a good flexible silicon glue, liberally coat the underneath of the fender where the patch will be located, and then use new zip ties to pull the fender and the patch together. if done properly, some silicone will come out of the holes, but that will mean that you have got a good, securely glued patch. wipe off the excess silicon, let it dry and then enjoy the fixed fender.
As an added note, there are red zip ties which blend in very well with Honda red plastic.
I have seen green zip ties as well, but they were bright green. I don't know what would work with your dark green, but any color of plastic would work okay since the patching piece will be on the underneath side of the fender.
You can also use the dark green Krylon paint for plastics to cover the patch and make it less noticeable. I have used that color on my Suzuki Vinson and it blends pretty well.
Remove fender..
Clean underside..
Line everything up like it is suppose to be..
Get short pieces of plastic like from a butter dish lid..
JB Weld across seam..
opps cracked my fender.
