the idle screw simply props open the slide a little bit, basically simulating a very slight twist of the throttle. If you back it out far enough to where it doesn't touch the slide then it will have no effect until it is turned in (tightened) enough to contact the slide again. You should adjust your idle when the motor has warmed and the choke is off.
Do yourself a favor and pull the slide out of the carb and look down into the hole it came out of, you will see the end of the idle screw sticking out in there when it is screwed in enough, and can see the angled portion of the slide that the idle screw impacts to prop it open. Make sure the slide is re-inserted in the proper orientation. Very basic stuff.
Pulling the cap off the muffler will reduce back pressure and allow the motor to breath more freely and will effect the air/fuel mix that is fed into your motor. You can accomplish the same thing (while leaving the muffler cap on) by tuning your carb instead of the muffler. Changes to the air filter will also have a similar effect...
All good advice. But I gotta tell ya. I yank that darned restrictive baffle out of all of my bikes. If I'm not running a combustion chamber, (Good ones are expensive,) I'll simply take out the baffle. And to try tuning a stock NT carb is almost pointless and a hit and miss proposition. At the very least a speed carb is a better option.
The other advantage to yanking the baffle is decibels. You can't deny that LOUD PIPES SAVES LIVES.
Yeah, Yanking the baffle is cheating a little, but it works.
fatdaddy.
IT'S YOUR BIKE, BUILD IT YOUR WAY.
And OH YEAH, Make sure the throttle cable is allowing the slide to go all the way to the bottom of the slide intake. You have adjustments at the throttle and at the carb top. If the slide isn't going all the way down then the idle adjustment screw won't do much good.
