My 1980 Kawasaki 750 Ltd is having idle problems. It starts up well but idles too high or to low . The rpms change as it runs every once in a while. I have trying adjusting the idle and the mixture screw but i cant figure it out. When I put the choke on the RPMS increase. IT also has a slow throttle response and it stays reved up high for a while . It doesnt come back to normal. I just need some suggestions on what to try.