I recently bought a 05 ninja 250 bike and when i first got it, the bike ran fine. it was great actually but then when i was riding one day it just started to bog down and die and i pulled over to a gas station and tried to fill up and it was still under half full. it took 5 to 10 min to start back up and run good again so i took it home and then short time after like day wise it would start to be slow when i gassed it to get up to speed. like it was a slow response time or something im not really for sure. but it is slow and it tops out at 75 mph with the throttle all the way open. it just wont go any faster and im not sure what else to do about it. ive cleaned out the carbs new spark plugs changed the oil put new gas in it after i cleaned the carbs and im just not sure? any help guys?!

Welcome to our site, Sam !!!

First thing to check is under your seat for any obstruction to the intake of the air filter.
While you are there, pull that filter and wash it in warm water with detergent, dry it and put some oil on it and replace it.

Next, check that all the fuel filters are clean and that your tank's cap vents properly.

Welcome Sam!

sounds like the float valves are gummed up

If your intake vents are clear, it still sounds like a carb issue. Its easy to miss the hidden jets and passages if its your first time inside one. Also, the float level could be off on one of them. The sync could also be off.

If it was running good and then suddenly isn't, the carbs are the likely culprits. Or possibly the fuel screen is plugged. Wouldn't hurt to clean it.

Sometimes people go into the carbs, clean them and then put them back together with silicone sealer. That makes the bike run good for a few days and then the silicone gums up everything when it dissolves. Look for silicone around the bowl gasket areas to see if the previous owner did that.

alright i will have to check that stuff out and what about the fuel cap? cause one day i was riding and i stopped and didnt have a helmet on and i heard a sounded like whisling or like pressure coming out? like the sound you hear when you open up a pop botle and i dont know if i need to replace it or if its not harming anything?

Will it rev cleanly up to redline in lower gears?

As noted, a blocked intake snorkel will cut your power as the revs increase.

If the tank is not venting it will run fine after sitting a while, then slowly lose power as you ride.

You could drain the float bowls into something and take a look at what comes out. Do that with the gas off. Also pull the line off the petcock and confirm that you are getting a good flow of fuel.

There are also screens and filters in the fuel line that could be partially clogged.

Will it rev cleanly up to redline in lower gears?

As noted, a blocked intake snorkel will cut your power as the revs increase.

If the tank is not venting it will run fine after sitting a while, then slowly lose power as you ride.

You could drain the float bowls into something and take a look at what comes out. Do that with the gas off. Also pull the line off the petcock and confirm that you are getting a good flow of fuel.

There are also screens and filters in the fuel line that could be partially clogged.

ok the intake snorkel? whats that and yeah if it sits after it warms up it runs good in low gears staying below 8000 rpms once it goes higher then that it seems to just rev out i gues would be the way to explain it. but it does lose power adn i havnt taken my carb off yet but took the line off the tank and some weird stuff came out of the line and then when i turned the bike on and let some gas drain the gas in the tank seemed fine. the tank is a little rusted on the sides. one more thing it rained last night and when i went to check the tank today i had water on the inside of the gas hole like it was on the sides of it i dont know if it drained in my gas tank but what does that mean?

Here's a quick check you can do. Fire the bike up and while you're driving it vary the choke input and drive with the choke on. If the bike runs fine you know the problem is (at the least) within your carbs. If it runs the same it may not necessarily be outside the carbs but it does eliminate a lot of variables.

alright i will have to check that stuff out and what about the fuel cap? cause one day i was riding and i stopped and didnt have a helmet on and i heard a sounded like whisling or like pressure coming out? like the sound you hear when you open up a pop botle and i dont know if i need to replace it or if its not harming anything?

Well if it's a constant whistle, most of us have that. There's a small vent hole at the top of your gas tank which 'whistles' , and the pitch goes along with the throttle. Normal :)

Here's a quick check you can do. Fire the bike up and while you're driving it vary the choke input and drive with the choke on. If the bike runs fine you know the problem is (at the least) within your carbs. If it runs the same it may not necessarily be outside the carbs but it does eliminate a lot of variables.

ok so while the bike is on turn the choke what to all the way open or what? and if it runs good and fast then its the carbs? and if it runs the same its not the carbs?