I have a 02 kx 85 when u ckoke the bike it runs choke off bike shuts off

a lot of new bikes have a automatic choke ,but if you look at the carburetor you should see 2 cables 1 is the throttle cable the other is the return cable both run up to the throttle hand control (some bikes might not have a return cable) if you see a third cable its probably the choke cable so you will need to follow it , sometimes it might not be a cable but a leaver on the side of the carbi , some cables run just under the seat or to the left handle bar depends .

possible blockage of fuel cap if after running you remove the fuel cap and there is a hiss of air rushing in then the cap breather is defective try running the bike with the cap off and see if it runs ok. if that is not it then possible dirt being lifted in the fuel tank. clean out the fuel tank ensure no dirt is getting into the fuel system if that is not the case then check the carborator, i dont think it is a heat problem to test remove line from tank to another fuel source tank and run the bike and see if you have the same issue. i hope this helped. do this in a well ventilated area due to fuel fumes and exhaust gas.

Well there are more questions to be asked. Is your bike all stock? What ratio of gas are you running? And have you made sure your carb is clean

She will loose power and possibly shut down if overheated. Check your cyclinder pressure. Make sure head didn't warp.

if the bike is to small for your the BEST thing to do is move up in bikes, if you can ride a 85 you'll have no problem on a 125, if your feet dont reach ground thats fine your are not on the ground when your flying in the air over that 100 foot double.
Good luck
M.Woodring

check all fuid levels , hold clutch handle in before cranking, always start in neutral, sit on bike
pull ckoke if it is cold outside all the way out until you here it start or backfire . If it backfires
push choke half way in, leave it there until bike is running well. As it warms up push choke all
the way in before riding , Always make sure your battery, and fuel are full charge and plenty
of gas , and chevron is one of the better fuel for your bike . It has techron in the fuel , and this
keeps system very clean . I hope I have helped ?????????

How to use your choke correctly. The choke is only to be used for starting a cold engine. If it is a lever, usually you pull it up for on , and push it down for off. look for some type off arrow, or up & down. To start your cold engine, turn on fuel tap, give full choke, turn key on and press starter or kick start, it is very important that you do not use the throttle while starting with the choke, just turn the key on, and press the starter with full ckoke, and no throttle. Once the bike fires and starts, turn down the choke a little and find a idle, after a few minits, you can turn off the choke and ride off. The use off the choke is only for starting a cold engine.

Check your spark plug. If it is not all black, it should be ok. If it is, replace it. Reinstall new plug, Kick it full choke no throttle. Let it run for 15 secs with the choke on. Shut the choke off while reving it. If the bike will not idle, clean the carb. Chaz Moto DC

Here are two solutions for you:
A - Take the carberator off and soak it in some good quality carb cleaner for about 1/2 an hour.  That should take care of any residue in the carbs.
B - Alternatively (and for the less technical minded) there is a great product called Sea Foam.  Try to find it at your local CSK auto/NAPA/Wal-Mart.  Pour a small amount (maybe 1/4 ounce) into each cylinder chamber (take out the spark plugs), try to pour a small amount into the carbs (a turkey baster works great for this), and pour the rest into the gas tank.  Let it sit for 5-10 minutes, then start it up.  *NOTE - the bike will start VERY hard at first until it burns through what's in the cylinders.  ALSO the fumes will be EXTREMELY strong and suffocating - make sure you do this OUTDOORS preferably, or at least in a VERY well ventilated area.
Good luck - I know how frustrating these things can be! :)
P.S. - I am a proud owner of a V-Star 1300 - great bikes! :)

hmmm, a few posibilities, might well be split cab diaphragms but overhaul should have spotted that. sounds like either too much gas or not enough, either flooding/gassing up or fuel starvation. could try running it without the aire filter too see what happens. it should run weak so if bike is better then you have too much gas, if bike worse then runnig weak to start with. I have seen this before with one particular cause.... petrol tap was leaking, gas runs past pistons when bike not running, soaks past and into crankcases. as breather recycles vapour back in to air box, when bike warm it's as rich sas hell. take of oil filler cap on engine and have a good sniff. you should smell only oil, if it's a strong smell of petrol, change oil and filter, dump petrol tap or see if new seals available.