97 had the old EVO engine, which its normal to warm up slowly. They run cool, and it takes a while for the heads to heat up and the heat to actually get to the carb. It takes a while for mine to warm up as well. I don't choke it that long though, instead i'll choke it (enricher) for the first 2-3 mins until the idle changes a little. Then let it warm up another 4-5 mins with the throttle lock on before i take off. The old EVO engine really needs to warm up before you take off, or you will start blowing seals and leaking oil.
Now i'm not saying the carb isn't dirty. However i don't think seafoam is the best answer for this. Usually its just time to take it apart and clean it out good. If its pretty clean you might consider upping the pilot jet to a 45. (assuming you have a keihn CV carb). Generally a jetted carb on that engine will run a 45 pilot, and a 180 or 185 main, with the air mixture screw 2 and 1/2 turns out. However, that isn't a fix all jetting. There are a lot of variables that will affect what jets you should be running. Elevation, and exhaust will affect how your bike runs and how it should be jetted. Also, i'm assuming your bike is fairly stock, no cam etc.