Before you go out and buy another carburetor you should be able to remove the stuck hot start plunger by drilling a small hole in it and turning it free with an easy out. Some penetrating lube and heat around the area (with the carb removed and gas drained of course) will help. If this fails, the older carb will work on your bike. For optimum performance you will want to fine tune it with some minor jetting (fuel screw, main jet) but you will find that the smaller carb delivers smoother power. The larger carburetor that was spec'd on your bike delivered more top end power and was finicky to jet in certain situations. Finally, don't forget to lube your hot start cable from time to time.