Welding the nut to the broken bolt is your best bet. I've had to do this on other repairs. Once thing I would love to find is information on the setup of the carburetor for this engine. Currently I just have plugs blocking off all the ports. 'm tempted to just go and buy a new carb to I have something that I can work with. I don't understand why finding any information about the factory one is so hard.
I'm going to tighten up the belt again, and see if it will stay this time, else, I'm going to have to do a little research on summit and see if I can find a solution. I'm thinking an idler pulley would be the answer, but I will have to locate one that would work in this application. Any info someone else has is always welcome.
Course, if money was no object... This is about 1300 bucks...