idle question

[elbandtioCA]

so i just spent the weekend doing my first valve adjust.  it went smoothly and when i was done i synched the carbs using the homemade manometer that has been posted on here.  that also went well and i got the carbs synched well.  i put in new plugs and also changed the coolant. now the bike revs up very smoothly all the way to its redline and sounds smooth when it idles. 

but... despite the fact that it idles at a steady 1500rpm when it is warm, i've noticed a new behavior since i did the valve adjust/synch: when i'm riding and come to a stop it drops down to about 1000rpm, maybe less, and stays there for ten or fifteen seconds before coming back up to 1500 rpm idle.  any ideas about what causes this lull in the idle?  it didn't do this before, even though it idled rougher.  a friend suggested a vacuum leak, but i've checked with wd40 and that doesn't seem to be an issue.  does anyone have suggestions about what might cause this idle lull?   

[Banditmax]

usually it indicates a rich mixture at idle. If you try turning your pilot screws 1/4 of a turn in that may help.

[gsxr400 racer]

usually it indicates a rich mixture at idle. If you try turning your pilot screws 1/4 of a turn in that may help.

[elbandtioCA]

ok, i'll give that a try.  of course now that bike is running pretty nicely it just started raining again...

i've actually never messed with the pilot screws before.  do i need a special screw driver/tool for this?  and tightening the screw leans out the mixture, right? 

[GooseMan]

MY bike used to idle pretty slowly when cold or warming up...and then once warm, it would idle pretty fast (around 2000 rpm). So now I just make sure to set the idle when the bike is really warm...after an hour or so of riding.

That probably doesnt help at all...but thats my 2 cents!