I have to respectfully disagree with Duncan.
Since you say it is not an expensive bow, and it currently isn’t fun to shoot, what have you got to loose? It would cost you more to have it fixed by a bowyer, then it cost you to buy it…
If you want to learn about making a bow, this would be a good place to start without actually having to make one from scratch. If you aren’t “burning” to make a bow, then skip it.
You can reduce the weight of a glass bow in several ways. They all require a lot of sanding. If you have a belt sander, or palm sander, it would make it easier. But hand sanding, elbow grease, and time, will get you there. I would suggest you get a bow scale if you don’t have one. Otherwise, when checking the bow weight a bunch, you start fooling yourself. It’s also nice to see how much weight is shed with how much sanding. Thus you can predict how much more sanding you need to achieve your goal. Also, a good dust mask is mandatory. Fiberglass dust is hell on your lungs.
– you can narrow the limbs by sanding the sides (is the bow really narrow limbed? then this may not be an option)
– You can sand the belly corners near the riser, and out about 18 inches (makes it trapezoidal in cross section)
– You can sand the back corners near the tip and in about 18 inches. (makes it trapezoidal in cross section)
If it was me, I would do a little of all three, and check the draw weight often to see how things are progressing. After I had gotten within 3 pounds of my draw weight, I would check the tiller, and if necessary sand the belly of whichever limb needed adjusting.
Whew, that sounds like a lot of work 😆