What to do to get my cr to idle ????

make sure your reeds are in right...they're between the carb & cylinder...they need to be "very" good condition...

fuel settings, something up with choke mechanism, check there first.
Is it manual choke? if it is try starting it a few times with no choke then gradually increasing. If it isn't then try setting the idle a touch faster or slower depending on how it sounds when it is running at temperature

You need to take it back apart and follow the float level setting directions to the letter.

The float level is very critical.

Also check and make sure you have the needle and seat installed properly.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

your carb: of course your carb has an idle and a mixture screw built-in. the idle is the knurled (usually gold) screw with the spring on it. and the mixture screw is the small one (usually gold too) set into the carb body. you'll know it because it's not hoding anything on. just sitting in the body. turn it only 1/4 turn at a time. your slide-needle should be mid to down if anything. c-clip up and needle down, that is. you want it to run as lean as possible w/o doing damage of course. almost all amateur's bikes run WAY too rich, all the time.
if you ever look at the starting line of a pro race compared to a local one, you'll be amazed. there's no smoke coming from a pro's bike. let your bike run a little hotter and cleaner and change the piston and rings more often. you and your bike will be happier couple.
a good way to test how your bike is running is to get it hot then run it wide open in fourth gear and hit the kill switch (if it still has one) while you still have it pegged. take the plug out and check the color. it should be light tan to pretty clean. any darker and your losing power. (don't use a new plug when you do this). are you getting a good spark? use the best plug you can get for your bike too. if your carb has adjustment for low, mid, and high end, then you should do it three times. at those three throttle speeds.
ATAC: are you sure you're going to remove the ATAC-valve system? if not then let me know. there are things you should know and do to make sure it's working right. it works very well if maintained and adjusted correctly.

as far as how it runs...it should absolutely rip. i was riding a cr 250 back then, but even a 30-year old 125 should scare you if it's running right. of course the piston and rings sounds like your major issue, but make sure it's breathing and flowing clean from airbox to silencer. are you replacing the silencer along woth the pipe?

Boyessen reeds are still your best bet. make sure your not sucking any air in through your intake manifold too. if it's old and cracked, then that could be why it was running too hot. of course make sure the surfaces on the manifold and the cylinder are in good shape and that no air can get sucked-in between them. a medium-depth scratch on the length of the seal surface can be bad.

i switched from kx's to yz's to cr's through the 80's and i loved the hondas. even managed a 4N (4th in the nation) plate on the cr. have fun and go fast! (don't ride over-your-head though) :)
i know every screw, spoke, and gasket of your bike and how it works like the back of my hand. if you have any other questions, plz feel free. i have lots of little factory-mechanic tips to help make your bike faster always stays in perfect shape, if you're interested.

cheers!

Your carberautor is either gummed up or needs to be adjusted. Begin by going to an auto zone or similar store and gatting a can of carb. cleaner that gets added to your gas. Be sure to follow the instructions on how much you add per gallon. let that run through your bike for a while and see where you are. If cleaning the carb. doesn't hellp, then the carb. will have to be adjusted.

TURN THE IDLE ADJUSTING SCREW ON THE CARB.

idle air control ( IAC) when you start our car and give gas it goes fine hold the gas pedal a little bit its should start faster that typcical iac but sometime egr vale might be sticking start our car hir the egr valve with hammer no to hard it should free it up thanks pierre