I have a 88 suzuki quadracer 500 . for about 10 years the pilot air screw has alway's been turned out 1and half to 1 and 3/4 . but here recently it acts like it doesn't want to idle down unless I put it in gear and slowly release the clutch . the only way it run's correctly is to turn the pilot screw 1/4 turn out . like this it run's like alway's but I know it's not right . I have racked my brain , if anybody has any suggestions I would greatly appreciate it . thanks

 

Have you cleaned the carb?
Checked for air leaks?
I'm thinking air leaks.

 

Yes I have cleaned the carb. several times. I have also done leak test pressure and vacuum. 1/4 turn out with the pilot screw and it run's like a zilla is suppose to run. It's bored .60 over and has a FMF Fatty pipe and FMF Silencer