My 2004 rmz 250 overheating

If it was white smoke coming out you may have blown a head gasket. If it is water cooled and there are no signs of external leakage then it only has one other way to go, inside.
If you have an oil dipstick, pull it out and check to see if your oil looks more like a milk shake sludge. Even if you can't see it, try dumping your oil from the sump and take out your oil filter. (unless it is a 2 stroke)

sounds like the timing has sliped out a bit,,,check it first

The rmz and kxf 250 2004-05 is a shame for both suzuki and kawasaki, they worked together to create a 4 stroke engine but failed.The first thing to brake is the waterpump. So everybody has to buy a new waterpump, but not the original one because it was a failure, they all broke and some motors got destroyed. The second thing is the valves and you can mostly reshim them once and then you would have to buy new ones that will also fail after a little use.The last thing that i know of is the camsaft, both the camsaft and valves are weak and wont tolerate any heat and you cant really ride the bike like a real offroad bike.
This is my personal experience.When i bought my bike, everything in the motor had been replaced. Probably because the waterpump failed.Nothing was wrong with it and it was great, great in cold starts and the motor ran great. But after 2 rides 10 hours tops it was hard to start, so i went to the suzuki dealers and they checked the time, set the carbonator and reshimmed the valves.The motor ran for 5 minutes and then was just the same as before. Then they told me that i would have to get new valves.But then i went to check around and everyone that i asked something about these bikes said that i should have asked them before i bought the bike so they could have told me that these bikes will never work properly.And here in iceland it's better for me to throw my bike away and buy a new one, a bike that is not older then 2006.
Its costs 250 dollars just to reshim the valves and set the carbonator.New valves cost around 520 dollars and the suzuki dealership takes around 280 dollars for the work of installing the new ones.

http://www.bikebandit.com/suzuki-motorcycle-rmz250-2004/o/m6667

Here is a link to bike bandits carb page for the rmz. Looks like the stock pilot is 35 and the main is 168, it looks like there are two other jets too, starter and power.

try spark plugs first

ya i have a yz250f and learned from a first hand experience that any racebike 2 stroke or 4 stroke doesnt like to idle for a few minutes without moviing. i started up my bike and let it sit for 8 minutes to warm up and antifreeze started spewing out. so i cut it off and called a friend that races. he told me these bikes need air moving through them otherwise they overheat easily and the antifreeze over flows because it expands. if i actually read the manual the book says not to let the bike stand and idle for more then 3 minutes cause after that amount of time it should already be warmed up.
so its just the bike over heating and make sure to top off your coolant the next time u ride

Check the thermostat in the bike it may not be opening at all sounds like it is not working and also check the water pump as well

Several things here. Do an oil change, 10w40 motor oil. Run premium gas and install a new NGK spark plug one heat range colder than stock. It sounds like you have an air leak causing a lean fuel mix. Check the carb mount bolts and the intake manifold bolts for tightness. Also set the valve clearances with a cold engine > .002 intake and .003 exhaust. Check for any cylinder head leaks. This would show up as oil on the cooling fins at the base of the cylinder head. Tighten the head bolts if needed.